BOOKS   BY   DR.   FISCHER 

PUBLISHED   BY 

JOHN  WILEY  &  SONS,  Inc. 


The  Physiology  of  Alimentation. 

viii  +  348  pages.  5J  by  8.  30  figures.  Cloth. 
$2.00  net. 

Fats  and  Fatty  Degeneration. 

A  Physico-chemical  Study  of  Emulsions 
and  the  Normal  and  Abnormal  Distribution 
of  Fat  in  Protoplasm.  (With  DR.  MARIAN 
O.  HOOKER.)  viii  +  155  pages.  6  by  9.  65 
figures.  Cloth.  $2. 00  net. 

Oedema  and  Nephritis. 

A  Critical,  Experimental  and  Clinical  Study 
of  fie  Physiology  and  Pathology  of  Water 
Absorption  in  the  Living  Organism.  Third 
and  Enlarged  Edition.  xvi+  922  pages.  6  by  9. 
217  figures.  Cloth.  $10. 00  net. 

Soaps  and  Proteins. 

Their  Colloid  Chemistry  in  Theory  and  Prac- 
tice. (With  GEORGE  D.  MCLAUGHLIN  and 
DR.  MARIAN  O.  HOOKER.)  ix  +  272  pages. 
6  by  9.  114  figures.  Cloth,  $4.00  net. 

TRANSLATIONS 
Physical  Chemistry  in  the  Service  of  Medicine. 

S^v^n  Addresses  by  DR.  WOLFGANG  PAULI, 
Professor  in  tho  Biological  Experimei  t 
Station  in  Vienna.  Authorized  Translation 
by  DR.  MARTIN  H.  FISCHER,  ix  +  156  pages. 
5  by  7J.  Cloth.  $1.25  net. 

An    Introduction   to  Theoretical    and    Applied 
Colloid  Chemistry. 

Five  Lectures  by  DR.  WOLFGANG  OSTWALD, 
Professor  in  the  University  of  L  inzig. 
Authorized  Translation  by  DR.  MARTIN  H. 
FISCHER,  xiv  +  232  pages.  6  by  9.  45  figures. 
$2. 50  net. 


SOAPS  AND  PROTEINS 

THEIR  COLLOID  CHEMISTRY 
IN    THEORY   AND   PRACTICE 


BY 

MARTIN  H.  FISCHER 

Doctor  of  Medicine 
Eichberg  Professor  of  Physiology  in  the  University  of  Cincinnati 

WITH   THE   COLLABORATION    OF 

GEORGE  D.  MCLAUGHLIN 

Formerly  research  Associate  in  Physiology  in  the  University  of  Cincinnati 

AND 

MARIAN  O.  HOOKER 

Doctor  of  Medicine 
Formerly  Instructor  in  Physiology  in  the  University  of  Cincinnati 


NEW  YORK 

JOHN  WILEY  &  SONS,  INC. 

LONDON:    CHAPMAN   &   HALL,  LIMITED 

1921 


COPYRIGHT,  1921, 

BY 
MARTIN  H.  FISCHER 


TO 

H.  C.  M. 

IN  AFFECTION,  ADMIRATION  AND  GRATITUDE 


450350 


".  .  .  thou  thyself,  a  watery,  pulpy, 
slobbery  freshman  and  new-comer  in  this 
Planet,  saitest  muling  and  puking  in  thy 
nurse's  arms;  sucking  thy  coral,  and 
looking  forth  into  the  world  in  the  blankest 
manner,  what  hadst  thou  been  without 
thy  blankets  and  bibs,  and  other  nameless 
huttsf  "— THOM AS  CARLYLE. 


PREFACE 


THE  studies  on  soaps  detailed  in  these  pages  were  originally 
undertaken  for  the  elucidation  of  various  purely  biological  ques- 
tions. The  proof  that  widely  differing  theoretical  and  practical 
problems  associated  with  the  maintenance  of  normal  physiology 
in  plants  and  animals  or  in  the  treatment  of  their  diseases  are 
essentially  problems  in  colloid-chemistry  (more  particularly 
problems  in  the  colloid-chemistry  of  the  proteins)  made  more 
and  more  evident  the  necessity  for  a  better  understanding  of  the 
nature  of  various  colloid-chemical  changes  themselves.  The 
chemistry  of  the  proteins  as  chains  of  widely  differing  amino- 
acids  presented,  however,  such  an  infinity  of  possible  variables 
that  every  direct  attempt  to  analyze  their  colloid-chemical 
behavior  was  beset  with  difficulty.  For  this  reason  we  turned 
to  the  soaps,  for  these  substances  not  only  contain  a  more  con- 
trollable number  of  purely  chemical  variables,  but  their  colloid- 
chemical  behavior  is  much  like  that  of  the  proteins.  From  the 
surer  ground  of  the  soaps  it  was  then  possible  to  step  over  into 
the  more  slippery  one  of  the  proteins.  What  are  some  of  the 
bearings  of  our  various  conclusions  upon  the  biological  behavior 
of  living  cells  under  normal  and  abnormal  circumstances  is  detailed 
in  the  pages  that  follow. 

The  reason  why  this  volume  is  written  as  it  is,  is  largely  the 
fruit  of  circumstance.  While  my  first  interests  are  biological 
and  medical,  it  happens  that  generous  friends  have  often  asked 
me  to  present  the  work  contained  in  this  and  some  other  of  my 
books  before  their  societies  devoted  to  various  branches  of  pure 
and  applied  chemistry.  Due  to  such  encouragement  I  have  set 
down  in  this  volume  the  substance  of  what  was  said  to  them  and 
in  which  they  saw  relations  to  their  own  fields  of  endeavor. 

Among  the  scientific  journals  to  which  this  work  was  first 
submitted  only  Science  and  The  Chemical  Engineer  could  find 


Vi  PREFACE 

space  for  some  of  its  fragments.  In  order  that  the  whole  might 
be  presented  in  sequential  form  it  was  therefore  necessary  to  write 
a  book. 

I  am  greatly  indebted  to  DORIS  WULFF  for  her  attention  to 
the  manuscript;  to  JOSEPH  B.  HOMAN  for  his  pen  and  ink  draw- 
ings; to  JOSEF  KUPKA  for  his  photographs  and  tireless  devotion 
to  the  business  of  the  day. 

MARTIN  H.  FISCHER. 
EICHBERG  LABORATORY  OP  PHYSIOLOGY, 
UNIVERSITY  OF  CINCINNATI, 
November  24,  1920. 


TABLE  OF  CONTENTS 


PART  ONE 
THE  COLLOID-CHEMISTRY  OF  SOAPS 

PAGE 

I.  Soap  Making 3 

1.  Introduction 3 

2.  Soap  Making  as  a  Colloid-Chemical  Problem.     The  Fatty 

Acids  of  the  Technical  and  Theoretical  Chemists 6 

H.  The  System  Soap/Water 9 

1 .  Introduction 9 

2.  Preparation  and  Gelation  Capacities  of  Some  Pure  Soaps  with 

Water 10 

a.  Soaps  with  Different  Basic  Radicals 10 

6.  Soaps  with  Different  Acid  Radicals 15 

c.  The  Effects  of  Water  Concentration 22 

III.  The  System  Soap/ Alcohol 30 

1 .  Introduction 30 

2.  Experiments  with  Monatomic  Alcohols 30 

a.  Monatomic  Alcohols  of  the  General  Composition 

CnH2n+1OH 30 

6.  Monatomic  Alcohols  of  the  General  Composition 

C«HMOH 49 

3.  Experiments  with  Diatomic  Alcohols 50 

4.  Experiments  with  Triatomic  Alcohols  (Glycerin) 52 

IV.  The    System    Soap/X.     Colloid    Soaps    in    Other    Non-Aqueous 

"Solvents" 60 

V.  On  the  General  Theory  of  the  Lyophilic  Colloids 64 

1.  Historical  and  Critical  Remarks 64 

2.  Theory  of  Soap  Gels 69 

VI.  Definition  of  Hysteresis,  Swelling,  Liquefaction,  Gelation  Capac- 
ity, Solvation  Capacity,  Syneresis,  Sol 74 

VII.  On  the  Reaction  of  Soaps  to  Indicators 77 

VIII.  On  the  Physical  State  of  Soap  Mixtures 83 

IX.  On  Reversibility  in  Soaps 89 

X.  On  the  "Salting-out"  of  Soaps 93 

1.  On  the  "Salting-out"  of  Potassium  Oleate 93 

2.  Critical  and  Historical  Remarks 107 

a.  Introduction 107 

6.  Historical  Remarks  on  the  "Salting-out"  of  Soaps 110 

c.  On  the  Theory  of  the  "Salting-out"  of  Soaps 113 

3.  On  the  "Salting-out"  of  Different  Soaps 116 

vii 


viii  CONTENTS 


XI.  The  Foaming,  Emulsifying  and  Washing  Properties  of  Soaps 136 

1.  The  Foaming  Properties  of  Soaps 136 

2.  The  Emulsifying  Properties  of  Soaps 150 

3.  On  the  Theory  of  Foaming  and  Emulsification 154 

4.  The  Washing  Properties  of  Soaps 157 


PART  TWO 
THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE 

I.  Principles  of  Hot  and  Cold  Process  Soap  Manufacture 163 

1.  Introduction 163 

2.  The  Oils,  Fats  and  Waxes  Entering  the  Soap  Kettle 164 

3.  Significance  of  Some  Fat  and  Oil  Constants  for  the  Colloid- 

Chemistry  of  Soap 169 

4.  Hot  and  Cold  Process  Soap  Manufacture 170 

5.  The  Mixing  of  Fat  with  Alkali.     Initial  Emulsification 174 

6.  Concentration  of  Alkali,  and  Method  of  Adding  it  for  Saponi- 

fication 178 

7.  The  Changes  in  Soap  Systems  Consequent  upon  Cooling ....  180 

8.  The  Salting-out  of  Mixed  Soaps 181 

9.  The  Finishing  of  Soap 183 

10.  Some  Physical  Constants  of  Market  Soaps 186 

11.  The  Conversion  of  One  Soap  into  Another 190 

II.  Fillers  for  Soaps 192 


PART  THREE 

THE  ANALOGIES  IN  THE  COLLOID-CHEMISTRY  OF  SOAPS, 
PROTEIN  DERIVATIVES  AND   TISSUES 

I.  The  Chemical  and  Colloid-Chemical  Behavior  of  Fatty  Acids  and 
Their  Derivatives  and  the  Analogous  Behavior  of  "  Neutral" 
Proteins  and  Their  Derivatives 205 

1.  Introduction 205 

2.  The  Chemical  Behavior  of  the  Fatty  Acids  and  the  Analogous 

Behavior  of  the  Amino-Acids  (Neutral  Proteins) 205 

3.  The  System  Egg-Globulin/Water 209 

4.  The  System  Gelatin/Water 218 

5.  Supplementary  and  Critical  Remarks 222 

6.  On  Peptization  and  Coagulation 225 


CONTENTS  ix 

PAGE 

II.  On  the  Theory  of  Poisoning  by  Ammonium  Compounds  and  by 

Heavy  Metals 235 

1.  General  Remarks 235 

2.  Experiments  on  the  Conversion  of  Heavy  Metal  Proteinates 

into  Light  Metal  Proteinates 237 

3.  On  the  Nature  and  Relief  of  Heavy  Metal  Poisoning 240 

4.  Concluding  Remarks 243 


PART  FOUR 
APPENDIX 

I.  Physico-Chemical  Constants  of  Various  Fatty  Acids 253 

1.  Acids  of  the  Series  CnH2nO2.     Acids  of  the  Acetic  Series. ...  253 

2.  Acids  of  the  Series  CnH2n— 202.     Acids  of  the  Acrylic  or  Oleic 

Series 254 

3.  Acids  of  the  Series  CnH2R-4O2.     Open  Chain  Acids.      Acids 

of  the  Linolic  Series 255 

II.  Physico-Chemical  Constants  of  Various  Alcohols 256 

AUTHOR  INDEX 259 

SUBJECT  INDEX  . . 261 


PART  ONE 

THE  COLLOID  CHEMISTRY  OF  SOAPS 


SOAPS  AND  PROTEINS 


PART  ONE 
THE  COLLOID-CHEMISTRY  OF  SOAPS 


SOAP  MAKING 
1.  Introduction 

IF  there  are  included  in  the  definition  of  soap  all  those  com- 
pounds which  are  formed  when  a  metallic  base  (including  ammo- 
nium) is  united  with  a  fatty  acid  radical,  any  effort  to  emphasize 
their  wide  importance  is  largely  superfluous.  Not  only  do  various 
soaps  appear,  change  and  then  disappear  in  living  animal  and 
plant  cells  under  various  circumstances,  not  only  do  they  con- 
stitute, from  both  a  qualitative  and  a  quantitative  viewpoint, 
one  of  the  chief  interests  of  theoretical  and  practical  chemists, 
but  their  existence,  availability  and  properties  have  much  to  do 
with  the  very  esthetics  of  our  existence,  from  clean  clothes  to  the 
fine  arts. 

The  making  of  soap — even  when  carried  out  in  ton  lots  by 
the  modern  manufacturer — does  not  in  our  day  differ  materially 
from  the  methods  employed  by  the  pristine  housewife.  "  Fats  " 
and  "  oils  "  are  still  stirred  or  boiled  in  a  kettle  with  a  caustic 
alkali  of  some  sort.  The  modern  concept  of  what  happens  under 
such  circumstances  may  be  said  to  date  from  CHEVREUL,  who  in 
1815  showed  that  "  fats  "  and  "  oils,"  whether  of  plant  or  ani- 
mal origin,  are  compounds  of  fatty  acid  with  alcohol,  usually  the 
triatomic  alcohol,  glycerin.  When  such  compounds"  (esters,  in 
other  words)  are  treated  with  an  alkali,  double  decomposition 
ensues,  the  metallic  radical  uniting  with  the  fatty  acids  contained 

3 


:    -\  •.•'  SOAPS  AND  PROTEINS 

in  the  fat  or  oil  to  form  the  corresponding  soaps,  while  alcohol 
(glycerin)  is  split  off.  Expressed  graphically  and  for  a  single 
"fat": 


Glyceryl  stearate  +  sodium        =       sodium  stearate          +         glycerin 

hydroxid 

It  is  important  for  our  purposes  to  note,  first,  the  variables 
contained  in  the"  elements  constituting  the  reaction  mixture. 

There  is  (1)  the  fat.  While  all  the  fats  are  esters,  they  run 
the  gamut  in  mere  physical  attributes  from  the  extreme,  on  the 
one  hand,  of  liquids  not  unlike  water,  through  viscid  oils,  to  the 
extreme,  on  the  other  hand,  of  solids  like  "  waxes,"  which  can 
hardly  be  broken  with  a  hammer.  But,  from  a  chemical  point 
of  view,  it  is  obvious  that  these  may  also  differ  widely  from  each 
other  both  as  to  (a)  kind  of  fatty  acid  found  in  the  ester,  and 
(6)  kind  of  alcohol  united  to  the  fatty  acid.  Even  without 
embracing  the  theoretical  extremes  we  find  at  the  one  end  fatty 
acids  with,  say,  six  carbon  atoms  in  the  molecule,  while  at  the 
other  may  be  those  with  two  dozen.  The  alcohol  found  in  the 
fat  is  usually  glycerin,  but  diatomic  or  monatomic  alcohols  may 
take  its  place. 

A  second  variable  concerns  (2)  the  hydroxid  employed.  Since 
the  commoner  soaps  of  commerce  are  sodium  soaps,  sodium 
hydroxid  is  the  alkali  ordinarily  employed.  In  "  soft  "  soap 
manufacture  potassium  hydroxid  is  used,  for  the  soft  soaps  are 
potassium  soaps.  Directly  or  indirectly,  however,  other  hydroxids 
or  bases  are  of  much  scientific  or  technologic  importance.  Sodium, 
potassium  and  ammonium  are  of  significance  when  ordinary 
"  washing  "  soaps  are  under  consideration,  but  the  wide  distri- 
bution of  magnesium  and  calcium  compounds  in  various  "  waters  " 
makes  necessary  a  knowledge  of  the  properties  of  the  soaps  of 
these  metals  when  "  hard  "  waters  are  used.  The  importance 
of  the  heavy  metals,  like  zinc  and  lead,  becomes  apparent  when 
it  is  recalled  that  zinc  stearate  is  used  as  a  dusting  powder  in 
skin  affections  and  that  the  plastic  properties  of  lead  plasters 
and  of  various  paints  is  dependent  upon  the  lead  soaps  found  or 
formed  in  these  mixtures. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  5 

Another  variable  is  represented  by  (3)  the  water.  It  must 
be  constantly  borne  in  mind  that  soap  manufacture  is  carried  out  \^ 
in  the  presence  of  relatively  little  water.  As  ordinarily  expressed, 
soap  making  proceeds  in  a  highly  concentrated  reaction  mixture. 
Not  without  its  important  influence  is  the  presence  of  (4)  the  alco- 
hol (glycerin)  split  off  in  the  process  of  manufacture.  A  final 
variable  that  must  be  considered  in  the  ordinary  process  of  soap 
manufacture  is  (5)  the  temperature.  Many  soaps  can  be  made, 
and  are  made,  at  ordinary  temperatures  or  by  the  "  cold  "  proc- 
ess; more  commonly,  however,  they  are  "  boiled." 

The  so-called  TWITCHELL  process  of  soap  manufacture  differs 
from  the  above  only  in  the  fact  that  instead  of  the  neutral  fats 
(in  other  words,  glycerids  or  esters)  the  free  fatty  acids  are  used. 
In  this  process  the  original  fat  is  first  broken  into  fatty  acids  and 
glycerin,  and  the  separated  fatty  acids  are  brought  by  themselves 
into  the  soap  kettle.  To  them  is  then  added  an  appropriate 
hydroxid,  and  the  soap  is  made.  Fundamentally,  however,  the 
variables  in  the  reaction  mixture  are,  from  both  a  chemical  and  a 
physical  standpoint,  essentially  those  already  listed,  except  that 
glycerin  is  missing. 

The  conversion  of  a  neutral  fat  (or  of  a  fatty  acid)  into  soap 
requires  time.  However,  if  the  reaction  has  been  carried  to  com- 
pletion, and  if  no  excess  of  any  of  the  ingredients  has  been 
employed,  it  is  obvious  that  the  final  mixture  in  the  soap  kettle 
must  consist  of  (1)  water,  (2)  alcohol  (glycerin)  and  (3)  soap. 
The  soap  must  be  examined  (a)  from  the  point  of  view  of  the  fatty 
acids  which  it  contains,  and  (6)  from  that  of  the  basic  radical  or 
radicals  which  it  may  hold.  This  fundamental  process  of  soap 
manufacture  is  complicated,  however,  by  a  procedure  which 
introduces  a  new  variable  into  the  general  problem  and  which, 
in  consequence,  requires  special  analysis.  This  is  (4)  the  "  salting- 
out  "  process.  In  the  manufacture  of  the  ordinary  washing 
soaps,  for  example,  the  fat  with  its  added  alkali  or  the  fatty  acid 
with  its  requisite  alkali  is  boiled  until  soap  formation  is  assumed 
to  be  complete.  There  is  then  added  either  (a)  a  great  surplus  of 
the  alkali  (like  sodium  hydroxid)  or  more  commonly  (6)  a  neutral 
salt.  Usually  sodium  chlorid  is  shoveled  into  the  soap  kettle. 
As  generally  expressed,  the  excess  of  alkali  or  the  presence  of  the 
sodium  chlorid  makes  the  soap  "  insoluble  "  in  the  "  lye,"  where- 
fore it  "  grains  "  and  floats  to  the  top  of  the  boiling  soap  mixture. 


6  SOAPS  AND  PROTEINS 

In  commercial  soap  manufacture,  this  surface  layer  of  soap  (bring- 
ing with  it  a  certain  amount  of  water,  of  excess  alkali  or  salt,  and 
some  glycerin  if  the  TWITCHELL  process  is  not  the  one  employed) 
is  separated  from  its  lye,  is  permitted  to  cool  and  after  more  or 
less  handling  is  made  into  "  cakes  "  for  trade  purposes. 


2.  Soap  Making  as  a  Colloid-Chemical  Problem.    The  Fatty 
Acids  of  the  Technical  and  Theoretical  Chemists 

Until  the  eighties  of  the  last  century,  soap  itself  and  the  proc- 
esses of  its  manufacture  were  looked  at  from  a  purely  "  chemical  " 
point  of  view.  The  soaps  were,  in  other  words,  regarded  as  ordi- 
nary salts  which  were  either  "  soluble "  or  "  insoluble "  in 
water  or  other  solvents.  When  soluble,  the  resulting  soap 
"  solutions  "  were  generally  regarded  as  obeying  the  laws  char- 
acteristic of  the  ordinary  solutions.  In  1888  FRANZ  HOFMEISTER  1 
chose  the  soaps  in  general  and  sodium  oleate  in  particular  as 
materials  of  "  colloid  "  nature  and  as  fit  substances  upon  which 
to  test  out  the  dehydrating  effects  of  various  salts.  The  notion 
that  soaps  were  "normal  electrolytes,"  that  solutions  of  soap 
follow  the  laws  of  osmotic  pressure  and  in  other  ways  comported 
themselves  as  true  solutions  continued,  however,  into  the  nineties, 
when  F.  KRAFFT  2  and  his  co-workers  pointed  out  that  the  more 
concentrated  solutions  of  soap  did  not  show  the  calculated  depres- 
sions of  the  freezing  point  or  elevations  of  the  boiling  point  of 
true  solutions.  KRAFFT  and  his  fellow  workers  therefore  declared 
these  more  concentrated  soap  solutions  "  colloid."  Further 
impetus  to  the  development  of  this  colloid-chemical  notion  of  the 
soaps  was  given  by  F.  GOLDSCHMIDT  and  his  pupils,3  while  various 
articles  subsequently  written  by  J.  LEIMDORFER;*  F.  BOTAZZI, 
C.  VICTOROW  5  and  W.  BACHMANN  6  may  be  said  to  have 
established  with  finality  that  the  soaps,  in  the  concentrated  form 

1  FRANZ  HOFMEISTER:  Arch.  f.  exp.  Path.  u.  Pharm.,  25,  6  (1888). 

»F.  KRAFFT  and  H.  WIGLOW:  Ber.  d.  deut.  chem.  Gesellsch.,  28,  2573 
(1895). 

»F.  GOLDSCHMIDT:  Kolloid-Zeitschr.,  2,  193,  227  (1908);  F.  GOLD- 
SCHMIDT  and  L.  WEISSMANN:  Kolloid-Zeitschr.,  12,  18  (1913). 

4  J.  LEIMDSRFER:  Kolloidchem.  Beihefte,  2,  343  (1911). 

•  F.  BOTAZZI  and  C.  VICTOROW:  Kolloid-Zeitschr.,  8,  220  (1911),  accessible 
only  as  review. 

•  W.  BACHMANN:  Kolloid-Zeitschr.,  11,  145  (1912). 


THE  COLLOID-CHEMISTRY  OF  SOAPS  7 

in  which  they  are  encountered  in  the  ordinary  processes  of  the 
soap  manufacturer,  represent  typical  colloid-chemical  systems. 

The  relationship  between  the  older  physico-chemical  views, 
which  proved  that  soaps  under  certain  circumstances  act  as 
"  normal  electrolytes,"  and  the  insistence  of  later  observers  that 
they  are  colloids  will  become  clearer  as  we  proceed.  Since  the 
"  soaps  "  ordinarily  discussed  are  mixed  soaps,  and  since  the 
properties  of  such  mixed  systems  are  in  themselves  dependent 
upon  the  nature  of  the  soaps  entering  into  these  mixed  systems, 
it  is  best  to  begin  by  an  investigation  of  the  physico-chemical 
properties  of  the  pure  soaps  themselves. 

It  is  well,  for  this  purpose,  to  list  the  fatty  acids  of  the  tech- 
nical and  theoretical  chemists.  This  is  done  in  the  following 
table  which  is  taken  from  J.  LEWKOwrrscH.1  Those  fatty  acids 
of  the  various  categories  which  receive  special  study  in  the  suc- 
ceeding pages  are  printed  in  bold  face. 

TABLE  I 

I.  ACIDS  OF  THE  SERIES  CnH2nO2.     ACIDS  OF  THE  ACETIC  SERIES 


Acetic  acid  ...................  CzIfcOz  Margaric  acid 

Butyric  acid  .......  .  ..........  C^sOz  Stearic  acid 

Valeric  acid  ...................  CsHioOz  Arachidic  acid 

Caproic  acid  ..................  CeHizOs  Behenic  acid 

Caprylic  acid  .................  CsHieOz  Lignoceric  acid 

Capric  acid  ...................  CioHzoOz  Carnaubic  acid 

Laurie  acid  ...................  CuH^O*  Pisangcerylic  acid  .............    CttH«8Oi 

Ficocerylic  acid  ...............  CuHzsOa  Cerotic  acid  ...................     CtsHnOi 

Myristic  acid  .................  CuHjgOi  Montanic  acid  ................     Ct8HMOx 

Isocetic  acid  ..................  CisHsoO*  Melissic  acid  .................     C»HwOi 

Palmitic  acid  ...........  ......  CieHuOi  Psyllostearylic  acid  ............     CnHMOi 

II.  ACIDS  OF  THE  SERIES  CnH2n_2O2.     ACIDS  OF  THE  ACRYLIC  OR 

OLEIC  SERIES 


Tiglic  acid  ....................  CeHsOz  Rapic  acid  ....................    CigHj4Oi 

Not  named  ...................  CuHzjOi  Petroselinic  acid.  ..............     CisHwOj 

Not  named  ...................  CuHzeOs  Cheiranthic  acid 

Hypogaeic  acid  ................  CuHaoOz  Liver  oleic  acid 

Physetoleic  acid  ...............  CwHjoOz  Doeglic  acid 

Palmitoleic  acid  ...............  CieHaoOi  Jecoleic  acid  (inferred) 

Lycopodic  acid  ................  CisHaoOj  Gadoleic  acid 

Oleic  acid  ....................  Cist^Oz  Erucic  acid  ...................     CaH«O» 

Elaldic  acid  ...................  CisHwOi  Brassidic  acid  .................     C»H«Oi 

Isooleic  acid  ..................  CigHwOi  Isoerucic  acid  .................     CuH«Oi 

1  J.  LEWKOWITSCH:    Oils,  Fats   and  Waxes,   5th   Ed.,    1,    111,   London 
(1913). 


8  SOAPS  AND  PROTEINS 

III.  ACIDS  OF  THE  SERIES  CnH27»-4O2 
(a)  OPEN  CHAIN  ACIDS 

(a)   Acids  of  the  Linolic  Series 

Linolic  acid  ...................    CisHttOz          Eheomargaric    (Elaeostearic) 

Millet  oil  acid  .................    CisHrcOz  acid 

Telfairic  acid  ................. 


Q3)    Acids  of  the  Tariric  Series 

Tariric  acid  ...................  CisHwOj 

(6)  CYCLIC  ACIDS.  ACIDS  OF  THE  CHAULMOOGRIC  SERIES 

Hydnocarpic  acid  ..............  CieHjgOj         Chaulmoogric  acid  ............. 

IV.  ACIDS  OF  THE  SERIES  CnH2n_6O2.     ACIDS  OF  THE  LINOLENIC  SERIES 

Linolenic  acid  .................  CisHsoOi          Jecoric  acid  (inferred)  ..........    CisHaoOs 

Isolinolenic  acid 


V.  ACIDS  OF  THE  SERIES  CnH2n-8O2.     ACIDS  OF  THE  CLUPANODONIC  SERIES 

Isanic  acid  ....................    CuHioOi         Clupanodonic  acid  .............     CisHzsOj 

Therapic  acid  (inferred)  ........    CnHjgOi          Arachidonic  acid 


VI.  ACIDS  OF  THE  SERIES  CnH2nO3.     HYDROXYLATED  ACIDS 

Sabinic  acid  ......  ............    CizHwOj          Not  named  ...................     CtiH«Oa 

Juniperic  acid  .................    CnHazOi          Cocceric  acid  .................     C«H«zOi 

Lanopalmic  acid  ...............    CuHwOj 


VII.  ACIDS  OF  THE  SERIES  CnH2n_2O3.     ACIDS  OF  THE  RICINOLEIC  SERIES 

Ricinoleic  acid  ................    CisHwOj          Ricinic  acid  ...................     CuHnOi 

Isoricinoleic  acid  ..............    CisHuOt         Quince  oil  acid  ................    CieHwOi 

Ricinelaldic  acid  .  .  .  .    .........    Ci»Hi4O» 

VIII.  ACIDS  OF  THE  SERIES  CnH2nO4.     Di  HYDROXYLATED  ACIDS 

Dihydroxystearic  acid  ..........    CisHiaCh          Lanoceric  acid  ................    CioH«oO« 

IX.  ACIDS  OF  THE  SERIES  CHH2n_2O4.     DIBASIC  ACIDS 

Heptadecamethylenedicarboxylic  Octodecamethylenedicarboxylic 

»cid  ...................    C^HwO*  acid  .......................    CjoHi«O« 

Japanic  acid  ..............    CiiH<oC>4 

With  these  remarks,  we  shall  proceed  at  once  to  a  study  of  the 
water-holding  power  of  various  pure  soaps. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  9 

II 

THE   SYSTEM   SOAP/WATER 
1.  Introduction 

In  the  course  of  our  work  on  the  stabilization  of  emulsions  l 
(in  which  we  showed  that  the  maintenance  of  a  water-in-oil  type 
of  emulsion  is  dependent,  in  the  main,  upon  the  substitution  of  a 
colloid  hydrate  for  the  pure  water)  we  were  struck  by  the  fact 
that  no  detailed  figures  are  available  which  discuss  in  any  syste- 
matic fashion  the  absolute  hydration  or  gelation  capacities  of 
various  pure  soaps.  Even  though  many  studies2  on  the  chem- 
istry of  soaps  and  their  general  colloid  behavior  are  available, 
and  even  though  we  possess  much  empiric  knowledge  regarding 
the  water  content  of  various  commercial  soaps,  these  investiga- 
tions deal,  for  the  most  part,  with  mixed  soaps,  with  soaps  pre- 
pared in  alcoholic  solution  or  with  such  as  have  been  "  salted- 
out."  But,  as  will  be  shown  in  this  and  subsequent  sections,  all 
these  circumstances  may  materially  modify  the  water-holding 
powers  of  the  involved  pure  soaps,  so  that  we  found  it  necessary 
for  our  own  purposes  to  prepare  pure  soaps  with  such  factors  elimi- 
nated. Since  the  values  which  we  have  obtained  are  not  only  of 
direct  chemical  and  technological  interest,  but  form  the  basis  for 
theoretical  views  covering  the  nature  of  the  lyophilic  colloid  state 
and  the  behavior  of  living  organisms  which  are  composed  of  such 
materials,3  we  give  below  our  detailed  findings.  First  to  be  dis- 
cussed is  the  system  composed  of  pure  soap  plus  water. 

1  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Science,  43,  468  (1916); 
Kolloid-Zeitschr.,   18,   129  (1916);    ibid.,   18,  242  (1916);    Fats  and  Fatty 
Degeneration,  29,  New  York  (1917). 

2  See  for  example  F.  HOFMEISTER:   Arch.  f.  exp.  Path.  u.  Pharm.,  25,  6 
(1888);  F.  KRAFFT  and  H.  WIGLOW:  Ber.  d.  deut.  chem.  Gesellsch.,  28,  2573 
(1895);    F.  MERKLEN:    Etude  sur  la  constitution  des  savons  du  commerce, 
Marseilles  (1906);    F.  GOLDSCHMIDT:    Kolloid-Zeitschr.,  2,  193,  227  (1908); 
J.  LEIMDORFER:    Kolloid-chem.   Beihefte,  2,  343   (1911);    F.  BOTAZZI  and 
C.  VICTOROW:    Kolloid-Zeitschr.,  8,  220  (1911),  accessible  only  as  review; 
W.  BACHMANN:    Kolloid-Zeitschr.,   11,   145   (1912);    F.  GOLDSCHMIDT  and 
L.  WEISSMANN:    Kolloid-Zeitschr.,  12,  18  (1913);    J.  LEWKOWITSCH:    Oils, 
Fats  and  Waxes,  5th  Ed.,  3,  299,  London  (1915). 

3  See  page  64;    also  MARTIN    H.  FISCHER  and    MARIAN  O.  HOOKER: 
Science,  48,  143  (1918);    MARTIN  H.  FISCHER:    (Edema  and  Nephritis,  3rd 
Ed.,  New  York  (1920). 


10  SOAPS  AND  PROTEINS 


2.  Preparation  and  Gelation  Capacities  of  Some  Pure  Soaps 

with  Water 

Unless  otherwise  noted,  we  prepared  all  our  soaps  in  exactly 
the  same  way,  namely,  by  neutralizing  a  definite  weight  (one 
mol)  of  the  pure  fatty  acid  with  a  chemically  equivalent  amount 
of  the  hydroxid,  oxid  or  carbonate  of  the  necessary  metal  in  a 
unit  volume  (one  liter)  of  water,  keeping  the  whole  mixture  at 
the  temperature  of  a  boiling  water  bath  until  union  between  the 
acid  and  base  had  been  accomplished.  Care  was  taken  to  prevent 
or  to  make  good  any  loss  of  water  from  the  reaction  mixture 
while  in  the  bath.  Under  these  circumstances  we  are  dealing  in 
the  end,  of  course,  only  with  a  unit  weight  of  some  pure  soap  in 
the  presence  of  a  unit  weight  of  water.  This  detail  regarding 
the  histories  of  their  preparation  is  of  little  interest  from  a 
"  chemical  "  point  of  view,  but,  since  the  soaps  are  "  colloid," 
it  is  of  vital  importance  from  a  physical  one  and,  therefore,  in  the 
elucidation  of  the  final  result  obtained.  After  we  had  prepared 
our  soaps,  the  reaction  mixtures  were  cooled  to  18°  C.  and  the 
yields  of  soap  weighed.  When  the  entire  mixture  became  gelatin- 
ous or  solid  we  considered  that  all  the  water  had  been  "  absorbed  " 
by  the  soap.1  When  "  free  "  water  began  to  appear  above  the 
soap,  the  weight  of  the  theoretical  yield  of  "  dry  "  soap  was  sub- 
tracted from  the  weight  of  the  soap  as  produced,  the  difference 
being  expressed  as  percent  of  water  "  absorbed  "  by  the  soap  in 
terms  of  the  weight  of  the  theoretical  "  dry  "  yield. 

a.  Soaps  with  Different  Basic  Radicals.  We  began  our  experi- 
ments by  preparing  a  series  of  linolates.  The  exact  experimental 
methods  followed  and  the  results  obtained  may  be  deduced  from 
Table  II.  The  striking  differences  in  the  absolute  amounts  of 
water  taken  up  by  these  different  soaps  is  readily  apparent  to  the 
naked  eye.  To  illustrate  the  matter  Fig.  1  is  introduced. 

The  different  water-holding  capacities  of  a  series  of  oleates  and 
stearates  is  shown  in  Tables  III  and  IV  and  Figs.  2  and  3.  The 
experimental  procedure  in  their  production  was  the  one  described 
above.  A  comparison  of  these  figures  and  findings  with  those 
obtained  in  the  linolate  series  is  of  interest  because  the  three  fatty 

1  This  is  really  not  the  case,  for  what  we  actually  determined  was  the 
gelation  point.  How  this  differs  from  the  hydration  (or  solvation)  point  will 
become  clear  later.  See  page  74. 


THE  COLLOID-CHEMISTRY  OF  SOAP§  /; 


SOAPS  AND  PROTEINS 


THE  COLLOID-CHEMISTRY  OF  SOAP§- 


acids  are  all  eighteen  carbon  atom  acids,  but  are  of  three  different 
series,  varying  in  their  degrees  of  hydrogenation  as  is  shown  in 
the  following  empiric  formulae: 


Linolic  acid  ..................... 

Oleic  acid  ...................... 

Stearicacid  ..................    Ci7H36COOH 


SOAPS  AND  PROTEINS 


In  Tables  V  and  VI  and  Figs.  4  and  5  are  shown  the  gelation 
capacities  of  a  series  of  palmitates  and  a  series  of  laurates. 

These  five  sets  of  experiments  show  that  a  first  factor  in  the 
amount  of  water  held  by  different  soaps  is  resident  in  the  nature  of 


the  metallic  radical  combined  with  the  fatty  acid.     If  the  radical 
most  effective  in  this  regard  is  given  first,  the  sequence  is  about 

as  follows: 

NH4,  K,  Na,  Li,  Mg,  Ca,  Hg,  Pb,  Ba  (?) 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


15 


As  reference  to  the  original  experiments  in  the  tables  shows,  it  is 
especially  the  last  mentioned  members  in  the  series  which  are 
likely  to  be  transposed. 


6.  Soaps  with  Different  Add  Radicals.  We  turned  next  to  the 
question  of  water  absorption  by  soaps  possessed  of  a  common 
base  and  prepared  under  identical  conditions  but  containing  differ- 


16 


SOAPS  AND  PROTEINS 


ent  fatty  acid  radicals.  The  re- 
sults in  the  case  of  the  sodium 
salts  of  the  acetic  acid  series  are 
shown  in  Fig.  6.  All  the  soaps 
were  so  made  that  in  the  end  one 
mol  of  the  soap  was  produced 
in  the  presence  of  one  liter  of 
water. 

As  Fig.  6  shows  (the  formate 
and  acetate  have  been  omitted) 
the  lowermost  members  of  this 
series  yield  only  molecular  ("true") 
solutions  under  these  experiment- 
al conditions.  The  solutions  of 
sodium  caprylate  and  caprate, 
as  here  prepared,  show  decidedly 
lasting  foams,  indicating  that  they 
are  approaching  colloid  proper- 
ties. Beginning  with  sodium 
laurate,  all  the  remaining  soaps 
yield  solid  white  gels. 

The  same  general  truths  are 
shown  for  the  potassium  salts  of 
the  acetic  acid  series  in  Fig.  7. 
Here  again  the  lower  members 
yield  only  "  true  "  solutions,  the 
middle  ones  liquid  colloids,  the 
upper  ones  solid  gels. 

These  two  groups  of  experi- 
ments show  that  under  otherwise 
fixed  conditions  the  water-absorbing 
power  of  any  soap  depends  upon 
the  nature  of  the  fatty  acid  in  the 
soap,  increasing  with  its  height  in  a 
given  series. 

To  get  a  more  accurate  meas- 
ure of  the  amounts  of  water  that 
can  thus  be  held  by  a  series  of  dif- 
ferent sodium  soaps  we  made  the 
following  experiment. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


17 


Molar  equivalents 
of  several  different 
sodium  soaps  of  the 
acetic  acid  series  were 
prepared  as  described 
above,  but  in  the 
presence  of  gradually 
increasing  amounts  of 
water.  Water  was 
added  until,  upon  cool- 
ing the  soap  mixture 
to  18°  C.,  a  solid  gel, 
or  one  not  showing 
"  syneresis,"  was  no 
longer  obtained. 
Stated  conversely,  it 
was  presumed  that 
the  limits  for  water 
absorption  had  been 
exceeded  as  soon  as 
we  obtained  only  a 
"  solution "  of  the 
given  soap  or  one 
which  showed  free 
liquid  at  the  tempera- 
ture chosen  (18°  C.). 

The  results  of  an 
actual  experiment  are 
portrayed  in  Fig.  8. 
The  lowermost  mem- 
bers of  the  sodium 
salts  of  the  acetic 
acid  series  take  up 
no  water  at  all;  they 
yield  only  "  true " 
solutions.  Sodium 
caproate  forms  a  true 
solution  in  very  little 
water,  but  when  this 
is  slowly  evaporated 


18 


SOAPS  AND  PROTEINS 


oo 

I 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


19 


one  does  not  always  get  a  crystalline  product.  The  residue 
is  frequently  shellac-like.  Sodium  caproate  may  therefore 
be  taken  as  the  first  soap  in  the  series  to  show  any  water- 
holding  power.  Sodium  caprylate  easily  yields  true  solutions, 
but  if  the  amount  of  water  is  chosen  correctly  a  beautiful 
gel  results  at  18°  C.  The  amount  of  water  for  one  mol 


3 

UTER 
0 


GELATION    CAPACITIES 

PER  MOL 
OF  DIFFERENT 
SODIUM   SOAPS 

WATER 


c  c,  c,  c.  c»  c.  c,  c4  c,  C* c,,  c* c,5   »c,5     c» CK,C» 


FIGURE  9. 

of  the  soap  must  not  exceed  200  cc.  The  matter  is  illus- 
trated in  the  left  hand  bottle  of  Fig.  8.  Sodium  caprate  still 
yields  a  solid  gel  if  500  cc.  of  water  are  present  to  the  mol  of  soap. 
This  is  shown  in  the  second  bottle  of  Fig.  8.  As  we  mount  in  the 
acid  series,  the  water-holding  capacity  grows  tremendously.  One 
mol  of  sodium  laurate  will  hold  4  liters  of  water;  the  same  amount 
of  sodium  myristate,  12  liters;  of  sodium  palmitate,  20  liters;  of 


SOAPS  AND  PROTEINS 

sodium  margarate,  24  liters;  of  sodium 
stearate,  27  liters  and  of  sodium  arachi- 
date,  the  enormous  value  of  37  liters. 
These  facts  are  illustrated  in  the  remain- 
ing bottles  of  Fig.  8  and,  in  graphic 
form,  in  Fig.  9. 

Sodium  margarate,  holding  its  24 
liters  of  water  to  the  mol  of  soap,  assumes 
its  rightful  place  in  the  acetic  series  as 
indicated  in  the  broken  line  column  of 
Fig.  9,  but,  since  it  does  not  seem  to  be 
settled  as  yet  that  margaric  acid  is 
more  than  a  "  eutectic "  mixture  of 
palmitic  and  stearic  acids,  this  point 
should  not  be  too  heavily  stressed.  The 
soap  of  pelargonic  acid  (Cg)  we  have 
not  yet  been  able  to  study.  Both  the 
sodium  and  potassium  salts  of  cerotic 
acid  (€27)  are  so  slightly  hydratable 

2  (even  after  subjection  to  high  tempera- 
tures and  increased  atmospheric  pressure) 

2  that  this  acid  does  not  fit  into  the  smooth 
series  of  the  soaps  already  described. 
Excepting  these  three  acids,  it  will  be 
noted  therefore  that  all  the  wafer-holding 
soaps  are  ot  acids  with  an  even  number 
of  carbon  atoms  in  the  empiric  formula, 
a  fact  which  may  not  be  without  signifi- 
cance in  deciding  which  of  the  acids  of 
the  empiric  formula  C«H2n+iCOOH  be- 
long in  a  true  series. 

In  the  experiment  just  described, 
the  water-holding  power  per  gram-mole- 
cule of  soap  was  determined.  In  order 
to  get  this  value  for  equivalent  weights 
of  the  different  soaps,  the  series  of 
experiments  illustrated  in  Fig.  10  was 
performed.  In  this  instance,  water  was 
added  to  one  gram  of  each  of  the  care- 
fully dried  sodium  soaps  until,  after 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


21 


solution  in  a  hot  water  bath,  a  dry  gel  was  no  longer  obtained 
on  reducing  the  temperature  of  the  mixture  to  18°  C.  It  is 
again  evident  that  only  liquid  mixtures  (true  solutions)  are 
obtained  upon  the  addition  of  even  trifling  amounts  of  water  to 


GELATION   CAPACITIES 

PER  GRAM 

OF   DIFFERENT 

SODIUM  SOAPS   WITH 

WATER 


C    C,  C3  C4  C5  C6  C7  C.  C,  C*  C,,  C .,  CI5  Cu  C,5  C,.  C,,  C.4  C,,Cja 

ZOOO-,  «2£0D 

-^2E55     i     °     2     fc     t<|     ? 
o      5      Z 


S0:^^ 


>o 


A.    rj  ^*,         -^ 
<<H       tf 

C2S     < 


FIGURE  11. 


the  lowermost  members.  The  actual  amounts  of  water  taken  up 
by  the  higher  members  per  gram  of  soap  are  shown  in  Table 
VII  and,  graphically,  in  Fig.  11. 

The  water-holding  capacities  of  three  sodium  soaps  of  the  oleic 
series  (oleate,  elaidate  and  erucate)  and  that  of  sodium  linolate 
are  shown  in  Fig.  12  and  Tables  VIII  and  IX.  These  two  tables 


22  SOAPS  AND  PROTEINS 

show  that,  in  the  oleic  series  also,  the  soap  of  the  higher  fatty 
acid  has  a  greater  absolute  gelation  capacity  than  a  lower  one. 

Because  linolic,  oleic  and  stearic  acids  differ  from  each  other 
only  in  the  degree  of  their  hydrogenation  it  is  of  interest  to  com- 
pare the  gelation  capacities  of  their  three  sodium  soaps.  The 
amount  of  water  in  cc.  held  per  gram  of  dry  soap  is  as  follows: 

Linolic  (C17H3iCOOH) 3.31 

Oleic       (CnHaaCOOH) 3.28 

Stearic  (Ci7H36COOH) 88.00 


FIGURE  12. 

When  comparison  is  made  of  the  amount  of  water  in  cc.  held 
per  mol  of  dry  soap,  the  values  are  as  follows: 

Linolic  (C17H31COOH) 1,000 

Oleic      (C17H33COOH) 1,000 

Stearic  (Ci7H36COOH) 26,928 

Or,  expressed  as  percent  of  soap  required  to  yield  the  described 
colloid  systems: 

Linolic 23 . 20  percent 

Oleic 23 . 31  percent 

Stearic 1.12  percent 

c.  The  Effects  of  Water  Concentration.  The  physical  state  of  a 
soap/water  system  has  in  the  above  paragraphs  been  shown  to 
be  dependent  upon  (a)  the  type  of  base,  and  (6)  the  type  of  fatty 
acid  in  the  soap.  We  wish  now  to  emphasize  the  fact  that  a  third 
element  in  the  matter  is  (c)  the  concentration  of  the  water.  This 
item,  which  will  be  considered  in  greater  detail  later  because 


THE  COLLOID-CHEMISTRY  OF  SOAPS 

of  its  importance  for  the  general  theory 
of  the  colloid  state,1  is  illustrated  for 
a  number  of  the  sodium  and  potas- 
sium soaps  of  the  fatty  acids  of  the 
acetic  series  in  Fig.  13.  Each  pair  of 
tubes  contains  10  cc.  of  a  half  molar 
"  solution  "  of  the  sodium  or  potassium 
salt  of  propionic,  butyric,  valeric,  cap- 
roic,  caprylic,*  capric,  lauric,  myristic, 
palmitic,  margaric  or  stearic  acid.  It 
will  be  observed  that  the  first  six  pairs 
of  tubes  from  the  left  all  contain  mobile, 
clear  liquids — in  other  words,  liquids 
that  look  like  true  solutions.  In  the 
seventh  pair  (laurates)  the  sodium  salt 
lies  as  a  colloid  mass  in  a  solution  of 
sodium  laurate  while  the  potassium 
salt  yields  only  a  solution.  In  the 
eighth  pair  (myristates)  the  sodium 
salt  yields  a  solid  white  gel  while  the 
potassium  salt  still  yields  in  part  a 
"  true  "  solution  with  a  colloid  mass 
lying  in  the  bottom.  Beginning  with 
the  palmitate  pair  and  through  the 
margarate  and  stearate,  only  solid  white 
gels  are  obtained.  This  experiment 
suffices  to  show  that  a  colloid  soap 
system  may  be  obtained  with  water  only 
when  the  concentration  of  the  water  is 
kept  sufficiently  low  and  that  when 
equivalent  concentrations  are  compared 
a  sodium  soap  becomes  colloid  sooner 
than  a  corresponding  potassium  soap. 
As  we  shall  see  later,  this  is  because 
potassium  soaps  are  more  soluble  in 
water  and  tend  in  consequence  to  yield 
molecular  (true)  solutions  over  higher 
ranges  of  soap  concentration  than  the 
sodium  soaps. 

1  See  page  69. 


24 


SOAPS  AND  PROTEINS 


TABLE  II 

GELATION  CAPACITIES  OF  DIFFERENT  LINOLATES  WITH  WATER 


Theoret. 

Ob- 

Percent 

Soap. 

How  prepared. 

weight  of 
dry  soap 
(m.  w. 

served 
weight  of 
soap 

Absolute 
amount 
of 

of 
gelation 

Physical 
state 

of 

expressed 

as 

gelation 

at 

18°  C. 

in 

pre- 

water. 

18°  C. 

grams). 

pared. 

Ammonium 

Warm  normal  ammonium 

297 

1297 

1000 

336 

Highly  vis- 

linolate 

hydroxid  solution  poured 

cid,  slight 

into  warm  linolic  acid 

ly  cloudy, 

yellow 

liquid 

Potassium 

Hot      normal      potassium 

318 

1318 

1000 

314 

Highly  vis- 

linolate 

hydroxid  solution  poured 

cid,   opal- 

into hot  linolic  acid 

escent, 

yellow 

liquid 

Sodium  lino- 

Hot    normal    sodium    hy-1        302 

1302 

1000 

331 

Highly  vis- 

late 

droxid    solution    poured 

cid.slight- 

into  hot  linolic  acid 

ly  cloudy, 

yellow 

liquid 

Magnesium 

Magnesium     oxid     stirred 

291 

399 

108 

37 

Yellow 

linolate 

into  hot  linolic  acid  and 

sticky 

hot  water  added 

mass 

Calcium  lin- 

Dry     calcium      hydroxid 

299 

404 

105 

35 

White 

olate 

stirred    into    hot    linolic 

flakes 

acid  and  hot  water  added 

Barium  lino- 

Dry      barium       hydroxid 

348 

380 

32 

9 

Dry  flakes 

late 

stirred    into    hot    linolic 

acid  and  hot  water  added 

Lead  linolate 

Litharge  stirred  into   hot 

382 

382 

382(7)* 

(0 

Sticky   yel- 

linolic acid  and  hot  wa- 

low mass 

ter  added 

*  This  observation  is  subject  to  question  because  of  the  possible  oxidation  of   the  fatty 
acid. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


25 


TABLE  III 
GELATION  CAPACITIES  OF  DIFFERENT  OLEATES  WITH  WATER 


Soap. 

How  prepared. 

Theoret. 
weight  of 
dry  soap 
(m.  w. 
expressed 

Ob- 
served 
weight  of 
soap 
as 

Absolute 
amount 
of 
gelation 

Percent 
of 
gelation 
water 
at 

Physical 
state 
at 
18°  C. 

in 

pre- 

water. 

18°  C. 

grams). 

pared. 

Ammonium 

Warm  normal  ammonium 

299 

1299 

1000 

Over 

Clear,  solid 

oleate 

hydroxid      stirred      into 

334.4 

gel 

warm  oleic  acid 

Potassium 

Hot  normal  potassium  hy- 

320 

1320 

1000 

Over 

Clear,  semi- 

oleate 

droxid    stirred    into    hot 

312.5 

liquid   gel 

oleic  acid 

Sodium    ole- 

Hot   normal    sodium    hy- 

304 

1304 

1000 

Over 

Clear,  solid 

ate 

droxid    stirred    into    hot 

328.9 

gel 

oleic  acid 

Lithium  ole- 

Lithium carbonate  stirred 

288 

1288 

1000 

Over 

White,  solid 

ate 

into   hot  oleic  acid  and 

347.2 

gel 

hot  water  added 

Magnesium 

Magnesium     oxid     stirred 

293 

510 

217 

74.0 

White  plas- 

oleate 

into   hot  oleic  acid  and 

tic     mass 

hot  water  added 

in  "free" 

water 

Calcium 

Calcium   hydroxid   stirred 

301 

380 

79 

26.2 

White  plas- 

oleate 

into   hot   oleic   acid   and 

tic     mass 

hot  water  added 

in  "free" 

water 

Barium 

Hot    normal    barium    hy- 

350 

360 

10 

2.9 

Yellowish 

oleate 

droxid    stirred   into    hot 

plastic 

oleic  acid 

mass      in 

"free" 

water 

Lead  oleate 

Lead  oxid  stirred  into  hot 

384 

425 

41 

10.7 

Yellowish 

oleic  acid  and  hot  water 

plastic 

added 

mass  °    in 

"free" 

water 

Mercury  ole- 

Yellow mercuric  oxid  stir- 

381 

425 

44 

11.5 

Yellowish 

ate 

red   into   hot   oleic   acic 

plastic 

and  hot  water  added 

mass      in 

"free" 

water 

26 


SOAPS  AND  PROTEINS 


TABLE   IV 

GELATION  CAPACITIES  OF  DIFFERENT  STEARATES  WITH  WATER 


Soap. 

How  prepared. 

Theoret. 
weight  of 
dry  soap 
(m.  w. 
expressed 

Ob- 
served 
weight  of 
soap 
as 

\bsolute 
amount 
of 
gelation 

Percent 

of 
gelation 
water 
at 

Physical 
state 
at 
18°  C 

in 

pre- 

water. 

18°  C. 

grams)  . 

pared. 

Ammonium 

Warm  normal  ammonium 

301 

1301 

1000 

Over 

White  plas- 

stearate 

hydroxid     stirred     into 

332.2 

tic  mass 

warm  stearic  acid 

Potassium 

Hot  normal  potassium  hy- 

322 

1322 

1000 

Over 

Semi-hard 

stearate 

droxid    stirred   into    hot 

310.5 

white 

stearic  acid 

soap 

Sodium 

Hot    normal    sodium    hy- 

306 

1306 

1000 

Over 

Hard  white 

stearate 

droxid    stirred   into    hot 

326.8 

soap 

stearic  acid 

Magnesium 

Magnesium    oxid    stirred 

295 

960 

665 

225.4 

Somewhat 

stearate 

into  hot  stearic  acid  and 

plastic 

boiling  water  added 

chalky 

mass      in 

"  f  ree" 

water 

Calcium 

Calcium   hydroxid  stirred 

303 

705 

402 

132.6 

White,  dry, 

stearate 

into  hot  stearic  acid  and 

brittle 

hot  water  added 

powder  in 

"free" 

water 

Barium 

Hot    normal    barium    hy- 

352 

587 

235 

66.8 

White 

stearate 

droxid    stirred   into    hot 

flakes    in 

stearic  acid 

"  free  " 

water 

Lead    stear- 

Litharge stirred  into   hot 

386 

730 

344 

89.1 

White.hard 

ate 

stearic  acid  and  boiling 

flakes     in 

water  added 

"  f  r  ee  " 

water 

Mercury 

Yellow  mercuric  oxid  stir- 

383 

865 

482 

125.8 

White 

stearate 

red  into  hot  stearic  acid 

flakes     in 

and  boiling  water  added 

"  f  ree  " 

water 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


27 


TABLE   V 

GELATION  CAPACITIES  OF  DIFFERENT  PALMITATES  WITH  WATER 


Theoret 

Ob- 

Soap. 

How  prepared. 

weight  01 
dry  soap 
(m.  w. 

served 
weight  o 
soap 

Absolute 
amount 
of 

Percent 
of 
gelation 

Physical 
state 

expressed 

as 

gelation 

water 

at 

in 

pre- 

water. 

at 

18°  P 

18°  C. 

grams). 

pared. 

lo      \*j. 

Ammonium 

Warm  normal  ammonium 

273 

1273 

1000 

Over 

Solid  white 

palmitate 

hydroxid      stirred      into 

366.3 

gel 

warm  palmitic  acid 

Potassium 

Hot  normal  potassium  hy- 

294 

1294 

1000 

Over 

Plastic 

palmitate 

droxid    stirred   into    hot 

340.1 

white  gel 

palmitic  acid 

Sodium  pal- 

Hot   normal    sodium    hy- 

278 

1278 

1000 

Over 

Solid  white 

mitate 

droxid    stirred    into    hot 

359.6 

gel 

palmitic  acid 

Magnesium 

Magnesium    oxid    stirred 

267 

440 

173 

64.8 

Rather 

palmitate 

into    hot    palmitic    acid 

brittle 

and  hot  water  added 

mass; 

plastic  at 

higher 

tempera- 

tures 

Barium  pal- 

3ot   normal    barium    hy- 

324 

670 

346 

106.8 

Dry,    flaky 

mitate 

droxid   stirred   into    hot 

masses 

palmitic  acid 

Lead  palmi- 

Jtharge  stirred  into   hot 

358 

390 

32 

8.9 

Shiny,  hard 

tate 

palmitic    acid    and    hot 

flakes  ; 

water  added 

plastic  at 

higher 

tempera- 

tures 

28 


SOAPS  AND  PROTEINS 


TABLE   VI 

GELATION  CAPACITIES  OF  DIFFERENT  LAURATES  WITH  WATER 


Soap. 

How  prepared. 

Theoret. 
weight  of 
dry  soap 
(m,.  w. 

Ob- 
served 
weight  of 
soap 

Absolute 
amount 
of 

Percent 
of 
gelation 

Physical 
state 
at 

expressed 

as 

gelation 

at 

18°  C. 

in 

pre- 

water. 

18°  C. 

grams). 

pared. 

Ammonium 

Warm  normal  ammonium 

217 

1217 

1000 

Over 

Semi-solid  ; 

laurate 

hydroxide     poured    into 

460.8 

solid     gel 

melted  lauric  acid 

at  0°  C. 

at  0°  C. 

Potassium 

Hot  normal  potassium  hy- 

238 

1238 

1000 

Over 

Like  water; 

laurate 

droxid   poured  into    hot 

420.1 

solid     gel 

lauric  acid 

at  0°  C. 

at  0°  C. 

Sodium  lau- 

Hot   normal    sodium    hy- 

222 

1222 

1000 

Over 

Solid  white 

rate 

droxid  poured    into   hot 

450.4 

gel 

laurio  acid 

Magnesium 

Magnesium    oxid     stirred 

211 

570 

359 

170.1 

White  flaky 

laurate 

into  hot  lauric  acid  and 

particles 

hot  water  added 

Barium  lau- 

Hot   normal    barium    hy- 

268 

510 

242 

90.3 

White    dry 

rate 

droxid    poured    into  hot, 

powder 

lauric  acid 

Lead  laurate 

Litharge  stirred  into   hot 

303 

425 

122 

40.2 

Hard,  white 

lauric  acid  and  hot  water 

mass; 

added 

plastic  at 

higher 

tempera- 

tures 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


29 


TABLE  VII 

GELATION  CAPACITIES  PER  GRAM  OF  SODIUM  SOAPS  OF  THE  ACETIC  SERIES 
WITH  WATER  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


Sodium  formate  
Sodium  acetate 

0 

o 

Sodium  propionate 

o 

$odiiirn  butyrftte 

o 

Sodium  valerate.  .  . 

o 

Sodium  caproate  
Sodium  caprylate  
Sodium  caprate  

1 

2 

cc.  (50.00) 
5  "    (28  57) 

Sodium  laurate  

18 

"      (6  26) 

Sodium  myristate 

48 

"      (2  04) 

Sodium  palmitate 

72 

"      (1  37) 

Sodium  margarate  . 

80 

"      (1  23) 

Sodium  stearate  
Sodium  arachidate  

88 
111 

"      (1.12) 
1      (0.89) 

TABLE  VIII 

GELATION  CAPACITIES  PER  GRAM  OF  SODIUM  SOAPS  OF  THE  OLEIC  SERIES 
WITH  WATER  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  colloid  system. 


Sodium  erucate  
Sodium  oleate  

60.00     (1.64) 
3.28  (23.36) 

Solid  white  gel 
Highly  viscid,  yellow  liquid 

Sodium  elaldate  '  

30.00     (3.23) 

Solid  white  gel 

TABLE   IX 

GELATION  CAPACITY  PER  GRAM  OF  A  SODIUM  SOAP  OF  THE  LINOLIC  SERIES 
WITH  WATER  AT  18°  C. 

Value  in  parenthesis  indicates  percent  of  soap  in  the  colloid  system. 


Sodium  linolate . 


3.31    (23.20)       Highly  viscid,  yellowish-brown  liquid 


30  SOAPS  AND  PROTEINS 


III 
THE   SYSTEM    SOAP/ALCOHOL 

1.  Introduction 

It  is  the  purpose  of  this  section  to  take  up  the  matter  of  the 
production  of  various  lyophilic  colloid  soap  systems  from  materials 
in  which  water  is  practically  or  entirely  absent.  The  facts  learned 
under  this  heading  will  then  serve,  with  the  experiments  described 
earlier  1  on  soap/ water  systems,  for  a  general  theory  of  the  lyophilic 
colloid  state.2 

Of  the  many  different  "  solvents  "  which  will  in  this  fashion 
yield  beautiful  lyophilic  colloid  systems  with  various  soaps,  we 
shall  first  take  up  the  various  alcohols,  for  not  only  do  alcohols 
(like  glycerin)  frequently  appear  in  the  processes  of  soap  manu- 
facture, but  this  or  some  other  alcohol  is  commonly  added  to 
soaps  from  without  to  make  them  "  transparent." 

2.  Experiments  with  Monatomic  Alcohols 

a.  Monatomic  Alcohols  of  the  General  Composition  CnH2n+iOH. 

1.  A  first  set  of  experiments  consisted  in  the  determination  of 
the  gelation  capacities  of  various  sodium  soaps  of  the  fatty  acids  of 
the  acetic  series  in  the  presence  of  absolute  ethyl  alcohol.  For  this 
purpose  we  proceeded  as  in  the  experiments  on  the  gelation 
capacities  of  these  soaps  when  water  was  the  "  solvent."  The 
soaps  were  made  by  adding  to  unit  molar  weights  of  the  various 
fatty  acids  the  necessary  chemical  equivalents  of  half  normal 
sodium  hydroxid  in  absolute  alcohol.  The  mixtures  were  kept 
in  a  water  bath  set  at  75°  C.,  and  enough  absolute  ethyl  alcohol 
was  then  added  to  each  until  on  cooling  the  soap-alcohol  mixture 
to  18°  C.  a  "  dry  "  gel  was  no  longer  obtained.  In  other  words, 
if  the  soap/ alcohol  system  remained  liquid  or  showed  "  syneresis  " 
it  was  held  that  its  gelation  limit  had  been  exceeded.  The  results 

1  See  page  9;  also  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER: 
Chem.  Engineer,  27,  155  (1919). 

*See  page  64;  also  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER: 
Science,  48,  143  (1918);  Chem.  Engineer,  27,  188  (1919). 


THE  COLLOID-CHEMISTRY  OF  SOAPS  31 

(which  are  readily  reproducible)  in  the  case  of  an  actual  experi- 
ment, are  shown  in  Figs.  14  and  15  and  in  Table  X.  The 
findings  detailed  in  Table  X  are  shown  graphically  in  Fig.  16. 

A  sodium  oleate-ethyl  alcohol  gel  prepared  under  identical 
conditions  is  pictured  in  Fig.  17. 

It  is  again  of  interest  to  note  in  connection  with  these  experi- 
ments in  which  ethyl  alcohol  is  used  that,  with  the  exception  of 
margaric  acid  (about  which  there  is  still  a  debate  as  to  whether 
or  not  it  is  more  than  a  eutectic  mixture  of  palmitic  and  stearic 
acids)  all  the  soaps  which  show  distinctly  lyophilic  properties 
are  those  of  acids  which  have  an  even  number  of  carbon  atoms  in 
the  empiric  formula.  This  fact  was  formerly  emphasized  in  the 
case  of  these  soaps,  when  water  was  the  "  solvent "  concerned. 

The  tendency  to  yield  colloid  gels  diminishes  not  only  quanti- 
tatively but  also  qualitatively,  as  we  descend  the  fatty  acid  series 
from  sodium  arachidate  to  sodium  acetate.  The  ethyl  alcohol 
gel  of  sodium  acetate  tends  to  crystallize  out  within  a  few  days 
after  its  formation.  The  butyrate  gel  (see  Fig.  14)  may  go  partly 
to  pieces  in  the  course  of  weeks,  unless  carefully  protected  from 
temperature  changes,  but  the  caproate  yields  a  lasting  colloid. 
These  lowermost  members  of  the  soap  series  with  an  even  number 
of  carbon  atoms,  however,  show  a  clean-cut  tendency  to  gel 
formation  not  a,t  all  apparent  with  the  formate,  propionate  and 
valerate.  In  the  case  of  the  last  named  substances,  repeated 
trials  under  the  conditions  of  our  experiments  yielded  only  thick 
crystalline  precipitates. 

It  is  further  to  be  noted  (Fig.  16)  that  the  regular  downward 
gradation  in  gelation  capacity  is  interrupted  in  the  series  between 
capric  and  caprylic  acids.  This  point  marks  the  transition  from 
the  fatty  acids  solid  at  ordinary  temperatures,  to  those  which 
are  liquid. 

2.  It  was  our  next  problem  to  discover  what  was  the  gelation 
capacity  of  some  picked  soaps  in  different  alcohols.  We  used  for 
this  purpose  several  sodium  soaps  of  the  acetic  acid  series,  three 
sodium  soaps  of  the  oleic  series  and  one  sodium  soap  of  the  linolic 
series.1  The  erucate  and  linolate  were  prepared  through  neu- 

1  The  matter  of  getting  absolutely  pure  fatty  acids  for  such  quantitative 
experiments  as  are  here  described  is  not  an  easy  one.  We  are  under  great 
obligation  to  the  Department  of  Organic  Manufactures  of  the  University  of 
Illinois  for  supplying  us  with  splendid  examples  of  the  different  fatty  acids 
used  in  this  study.  In  another  portion  of  the  work  we  used  Kahlbaum's  "K" 


32 


SOAPS  AND  PROTEINS 


tralization  of  the  necessary  molar  equivalents  of  acid  with  stand- 
ard aqueous  sodium  hydroxid  and  desiccated  over  sulphuric  acid 
at  37°  C.  The  remaining  soaps  were  similarly  prepared  but  dried 


at  90°  C.,  in  a  dry  air  oven,  to  constant  weight,  as  determined  by 
heating  a  test  fraction  to  110°  C. 

The  gelation  capacity  per  gram  of  the  sodium  soaps  of  nine 
different  fatty  acids  of  the  acetic  series  in  nine  different  mona- 

Brand  chemicals.  The  fact  that  the  fatty  acids  had  different  sources  explains 
some  of  the  slight  variations  in  the  numerical  values  obtained  in  different 
series  of  experiments.  It  should  be  noted,  however,  that  the  relative  values 
obtained  were  always  gotten  by  using  a  single  specimen. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  33 


34 


SOAPS  AND  PROTEINS 


tomic  alcohols  is  shown  photographically  in  Fig.  18  (A  and  E) 
and  graphically  in  Figs.  19,  20,  21,  22,  23,  24,  25  and  26.  The 
findings  are  compounded  in  Fig.  27.  In  each  instance  a  given 
weight  of  soap  had  more  and  more  of  the  various  alcohols  added 
to  it  while  in  a  warm  water  or  boiling  water  bath,  until,  upon 
reducing  the  temperature  of  the  reaction  mixture  to  18°  C.,  it 
would  no  longer  set  into  a  dry  gel.  The  actual  volumes  that  it 


GELATION   CAPACITIES    PER    MOL 
OF   DIFFERENT    SODIUM   SOAPS 

ETHYL-ALCOHOL 


a 

LITER 


I 


C     Ct  C3C«CSC.  C,  C.C,  CloCllC,tC1JCl4C,sCl4,CirCieC1,C2o 

sslSlI          S          £ 


FIGURE  16. 


was  found  possible  to  add,  while  still  accomplishing  this  end  are 
shown  in  Table  XI. 

The  tables,  figures  and  graphs  show  that  the  tendency  of  the 
various  soaps  to  yield  lyophilic  colloid  systems  grows  (1)  with  the 
complexity  of  the  soap  in  any  given  series  and  (2)  with  the  complexity 
of  the  alcohol  used  in  the  system.  The  only  exception  in  the  acetic 
series  is  represented  by  margaric  acid,  but  this  may  be  explained 
either  by  the  fact  that  it  is  an  odd  carbon  atom  acid  or  that  it 
represents  a  eutectic  mixture  of  stearic  and  palmitic  acids. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  /,       '    '  &6 

The  results  in  the  case  of  two  soaps  of  the  oleic  series  (sodium 
oleate  and  sodium  erucate)  with  this  series  of  alcohols  are  shown 
photographically  in  the  upper  two  rows  of  Fig.  28  and  graphically 
in  Figs.  29  (A)  and  30. 

The  behavior  of  sodium  elaidate  (elai'dic  acid  being  an  isomer 
of  oleic  acid)  is  shown  in  the  lowermost  series  of  bottles  of  Fig.  28, 
and  graphically  in  Fig.  29  (B).  The  gelation  capacity  of  this 
soap  differs  from  that  of  sodium  oleate  in  that  the  maximal 
gelation  capacity  is  obtained  with  an  alcohol  in  the  middle  of 
the  series.  In  general  all  the  gelation  capacities  lie  below  the 
values  obtained  with  sodium  oleate. 


FIGURE  17, 

The  experimental  results  covering  these  three  soaps  are  given 
in  Table  XII.  It  is  again  apparent  in  the  oleic  series  that  the 
gelation  capacity  increases  with  the  height  of  the  alcohol  in  the 
series;  while,  when  the  erucate  is  compared  with  the  oleate,  the 
former  has  a  higher  gelation  capacity  with  a  given  alcohol  than 
the  latter,  at  least  as  far  as  the  lowermost  members  are  concerned. 
We  were  not  successful  either  by  direct  or  indirect  means  (through 
primary  solution  in  methyl  alcohol)  to  get  gelation  values  in  the 
higher  alcohols  above  that  for  ethyl  alcohol.  We  cannot,  how- 
ever, say  at  this  time  whether  this  is  a  necessarily  correct  finding, 
for  our  erucic  acid  was  not  absolutely  pure. 


SOAPS  AND  PROTEINS 


FIGURE 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


37 


EB    HI     B    •  Jfc-  B     B 

•••  i 


BBS     B9 


•« 


•a   an    B  B 


^  and  5  of  Fig.  18  are  segments  of  the  same  picture.    The  vertical  rows  of  bottles  should  be 
read  upwards  as  a  continuous  series  in  both  instances. 


SOAPS  AND  PROTEINS 


GELATION    CAPACITY   PER    GRAM 

OF    SODIUM    CAPROATE 
IN   DIFFERENT  ALCOHOLS 


FIGURE  19. 


GELATION  CAPACITY  PER  GRAM 

OF    SODIUM    CAPRYLATE 

IN   DIFFERENT   ALCOHOLS 


(in 

FIGURE  20. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


GELATION  CAPACITY  PER  GRAM 

OF    SODIUM   CAPRATE 
IN   DIFFERENT   ALCOHOLS 


t  i 


FIGURE  21. 


GELATION   CAPACITY    PER   GRAM 

OF  SODIUM  LAURATE 
IN    DIFFERENT   ALCOHOLS 


FIGURE  22. 


40 


SOAPS  AND  PROTEINS 


GELATION  CAPACITY  PER   GRAM 

OF   SODIUM   MYRISTATE 
IN   DIFFERENT  ALCOHOLS 


FIGURE  23. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


41 


GELATION  CAPACITY  PER  GRAM 
OF   SODIUM   PALMITATE 
IN  DIFFERENT  ALCOHOLS 

1  !  i  I  i  II  if 

FIGURE  24. 


SOAPS  AND  PROTEINS 


GELATION  CAPACITY  PER  GRAM 

OF   SODIUM   MARGARATE 

IN   DIFFERENT  ALCOHOLS 


THE  COLLOID-CHEMISTRY  OF  SOAP& 


tec 

I7S 

GELATION  CAPACITY  PER  GRAM 
OF   SODIUM  STEARATE 
IN   DIFFERENT  ALCOHOLS 

ISC 
125 

'OC 
75 

5 

? 
C 

2     <     S 

FIGURE  26. 


44 


SOAPS  AND  PROTEINS 


GELATION  CAPACITY  PER  GRAM 

SODIUM  SOAPS  OF   THE 

ACETIC   SERIES   IN   DIFFERENT 

MONATOMIC  ALCOHOLS 


i  I 


H 


FIGURE  27. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


'45 


FIGURE  28. 


SOAPS  AND  PROTEINS 


GELATION   CAPACITY  PER   GRAM 

OF   SODIUM  OLE  ATE 
IN   DIFFERENT  ALCOHOLS 


cc 


GELATION    CAPACITY   PER   GRAM 

OF    SODIUM    ELAIDATE 
IN   DIFFERENT   ALCOHOLS 


cc 


Mill 


FIGURE  29. 


B 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


47 


GELATION   CAPACITY  PER   GRAM 

OF   SODIUM   ERUCATE 
IN   DIFFERENT   ALCOHOLS 


cc 


5    I    I 

a       <       u 


FIGURE  30. 


48 


SOAPS  AND  PROTEINS 


The  gelation  capacity  per  gram  of  sodium  linolate  in  different 
alcohols  is  shown  photographically  in  Fig.  31  and  graphically 
in  Fig.  32.  The  graph  is  based  upon  values  shown  in  Table 
XIII. 


FIGURE  31. 


GELATION  CAPACITY  PER  GRAM 

OF    SODIUM   LINOLATE 
IN   DIFFERENT   ALCOHOLS 


ll 


FIGURE  32. 


U  O  O 

I         Q         Z 


If  the  gelation  capacities  of  sodium  linolate,  sodium  oleate 
and  sodium  stearate  in  the  different  alcohols  are  compared,  read- 
ing horizontally  across  the  table,  it  will  be  noted  that  sodium 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


49 


linolate  shows,  on  the  whole,  a  lower  value  than  sodium  oleate 
and  the  latter  a  lower  one  than  sodium  stearate. 

It  was  noted  in  the  making  of  these  solutions  of  the  soap  in 
the  different  alcohols  that  the  soap  dissolved  first  in  the  lower 
members  of  the  alcohol  series  and  last  in  the  uppermost.  Upon 
lowering  the  temperature  the  gels  formed  first  in  the  upper  alco- 


FIGURE  33. 

hols  and  last  in  the  lowest  members  of  the  series.  It  should  be 
noted,  too,  that  the  solubility  of  sodium  oleate  in  methyl  alcohol 
is  so  high  that  slight  variations  in  temperature  are  sufficient  to 
cause  the  mixture,  in  the  concentration  here  used,  to  pass  from 
the  opalescent  gel  to  a  clear  solution,  while  a  lowering  of  the 
temperature  brings  it  back  to  the  gel  state.  As  we  ascend  to 


FIGURE  34. 

the  higher  alcohols  such  temperature  variations  must  be  made 
increasingly  larger  to  accomplish  the  same  result. 

6.  M anatomic  Alcohols  of  the  General  Composition  CnHnOH. 
Of  the  other  monatomic  alcohols  which  have  been  studied,  benzyl 
alcohol  yields  beautiful  soap  jellies  with  the  anhydrous  soaps  of 
both  the  acetic  and  oleic  series,  as  shown  in  Figs.  33  and  34,  as 
well  as  Tables  XIV  and  XV  which  contain  the  actual  experimental 
data. 


50 


SOAPS  AND  PROTEINS 


Cinnamyl  and  allyl  alcohols  yield  no  gels  with  either  of  these 
two  soap  series.  Sodium  linolate  yields  no  gel  with  benzyl 
alcohol  nor  with  cinnamyl  or  allyl  alcohol. 


3.  Experiments  with  Diatomic  Alcohols 

The  solvation  capacity  of  several  sodium  soaps  in  two  di- 
atomic alcohols,  namely,   trimethyleneglycol    (1,  3   propandiol) 


FIGURE  35. 


and  ethyleneglycol,  was  next   studied.     The  results  for  seven 
sodium  soaps  of  the  acetic  series  and  three  sodium  soaps  of 


FIGURE  36. 


the  oleic  series  with  trimethyleneglycol  are  shown  in  Figs. 
35  and  36,  and  Tables  XVI  and  XVII,  which  contain  the  ex- 
perimental data.  There  is  an  obvious  and  large  increase  in 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


51 


gelation  capacity  as  we  ascend  the  acetic  series.  Sodium  oleate 
lies  far  below  sodium  stearate  in  its  gelation  capacity,  while 
sodium  linolate  was  found  to  yield  no  gel  at  all.  Both  Table 
XVII  and  Fig.  36  show  that  sodium  erucate  and  sodium 
elaidate  (the  isomer  of  the  oleate)  have  a  Imver  gelation  capacity 
in  trimethyleneglycol  than  has  sodium  oleate,  but,  as  noted 
above,  we  were  not  completely  satisfied  with  the  purity  of  our 
erucic  acid. 


FIGURE  37. 

The  results  of  some  experiments  with  ethyleneglycol  and  some 
soaps  of  the  acetic  and  oleic  series  are  shown  in  Figs.  37  and  38. 
The  actual  experimental  findings  are  again  contained  in  Tables 
XVI  and  XVII.  As  apparent  from  the  figures  and  the  tables, 


FIGURE  38. 


only  the  higher  members  in  each  of  the  soap  series  will  yield  gels 
with  ethyleneglycol,  the  lower  members  yielding  only  true  solu- 
tions or  crystalline  deposits  in  the  cooled  reaction  mixtures. 


52 


SOAPS  AND  PROTEINS 


4.  Experiments  with  Triatomic  Alcohols  (Glycerin) 

The  solvation  capacities  of  four  sodium  soaps  of  the  acetic 
series  and  three  sodium  soaps  of  the  oleic  series  with  glycerin  are 


1    V 

•   * 


FIGURE  39 

illustrated  in  Figs.  39  and  40  and  Tables  XVIII  and  XIX.  Not 
only  does  the  oleic  series  stand  below  the  acetic,  but  in  both  series 
the  gelation  capacity  falls  rapidly  from  the  high  values  obtained 
with  the  upper  series  to  the  low  values  in  the  case  of  the  lower. 


FIGURE  40, 


Fig.  41  illustrates  the  system  sodium  linolate,  with  a  diatomic 
or  a  triatomic  alcohol.  When  these  mixtures  are  heated  to  the 
temperature  of  a  boiling  water  bath,  "  solution  "  occurs,  but  on 
cooling  the  mixtures  to  18°  C.  no  gelation  follows,  despite  their 
high  soap  content  (33.3  percent).  We  shall  return  later  to 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


53 


the    bearing    of    this    phenomenon    on    the   general    theory   of 
gelation. 

Fig.  42  shows  the  result  of  dissolving  1  gram  of  sodium  stearate 
or  sodium  oleate  in  50  cc.  of  allyl  alcohol  at  the  temperature  of 


FIGURE  41. 

boiling  water  and  then  cooling  to  18°  C.  At  the  higher  tempera- 
ture the  soap  dissolves  to  form  a  "  true  solution  ";  as  the  temp- 
erature falls,  the  soap  becomes  insoluble,  but  instead  of  forming 


FIGURE  42. 


a  gel  it  drops  out  as  a  crystalline  mass.  These  experiments  suffice 
to  show  that  not  every  soap  solvent  will  yield  a  colloid  system 
with  a  given  soap.  We  shall  use  these  facts  later  for  their  bear- 
ing upon  the  general  theory  of  colloids. 


SOAPS  AND  PROTEINS 


TABLE   X 

GELATION  CAPACITIES  OF  DIFFERENT  SODIUM  SOAPS 
WITH  ETHYL  ALCOHOL 


Soap. 

How  prepared. 

Theoret. 
weight  of 
dry  soap 
(m.  w. 
expressed 
in 
grams). 

Absolute 
amount 
ethyl 
alcohol 
absorbed 
(in 
liters). 

Percent 
of 
gelation 
alcohol 
at  18°  C. 

Physical 

state 
at 
18°  C. 

Sodium 
arachidate 

Arachidic  acid  dissolved  in  warm 
absolute  alcohol  and  \  normal 
NaOH  added  to  it 

334 

27.5 

8233 

White  gel 

Sodium 

stearate 

Stearic  acid  dissolved  in  warm  ab- 
solute alcohol  and  }  normal 
NaOH  added  to  it 

306 

21.0 

6863 

White  gel 

Sodium 
margarate 

Margaric  acid  dissolved  in  warm 
absolute  alcohol  and  i  normal 
NaOH  added  to  it 

292 

19.0 

6507 

White  gel 

Sodium 
palmitate 

Palmitic  acid  dissolved  in  warm 
absolute  alcohol  and  '  normal 
NaOH  added  to  it 

278 

18.0 

0475 

White  gel 

Sodium 
myristate 

Myristic  acid  dissolved  in  warm 
absolute  alcohol  and  ;  normal 
NaOH  added  to  it 

250 

15.5 

6200 

White  gel 

Sodium 
laurate 

Laurie  acid  dissolved  in  warm  ab- 
solute alcohol  and  |  normal 
NaOH  added  to  it 

222 

13.5 

6081 

White  gel 

Sodium 
caprate 

Capric  acid  dissolved  in  warm 
absolute  alcohol  and  ;,  normal 
NaOH  added  to  it 

194 

12.0 

6185 

White  gel 

Sodium 
caprylate 

Caprylic  acid  dissolved  in  warm 
absolute  alcohol  and  \  normal 
NaOH  added  to  it 

166 

5.0 

3012 

White  gel 

Sodium 
caproate 

Caproic  acid  dissolved  in  warm 
absolute  alcohol  and  }  normal 
NaOH  added  to  it 

138 

2.0 

1449 

White  gel 

Sodium 
valerate 

Valeric  acid  dissolved  in  warm 
absolute  alcohol  and  i  normal 
NaOH  added  to  it 

124 

No  lyoph- 
i  1  i  c 
proper- 
ties 

Crystalline 
precipitate 

Sodium 
butyrate 

Butyric  acid  dissolved  in  warm 
absolute  alcohol  and  i  normnl 
NaOH  added  to  it 

110 

1.0 

909 

White  gel 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


55 


TABLE   X— Continued 


Theoret. 

Absolute 

weight  of 
dry  soap 

amount 
ethyl 

Percent 
of 

Physical 

Soap. 

How  prepared 

(m.  w. 

alcohol 

gelation 

state 

expressed 

absorbed 

alcohol 

at 
18°  C. 

in 

(in 

at  18°  C. 

grams). 

liters). 

Sodium 

Propionic  acid  dissolved   in  warm 

96 

No  1  y  o  - 

Sticky      mix- 

propionate 

absolute   alcohol   and    i    normal 

philic 

ture,       ulti- 

NaOH added  to  it 

proper- 

mately crys- 

ties 

talline 

Sodium 

Acetic  acid  dissolved  in  warm  abso- 

82 

0.8(?) 

976  (?) 

White  gel 

acetate 

lute  alcohol  and  }  normal  NaOH 

added  to  it 

Sodium 

Formic    acid    dissolved    in    warm 

68 

Thick 

Crystalline 

formate 

absolute   alcohol   and    i    normal 

precipi- 

precipitate 

NaOH  added  to  it 

tate;  no 

lyophil- 

ic  prop- 

erties 

Sodium 

Oleic  acid  dissolved  in  warm  abso- 

304 

10.0 

3289 

White  gel 

oleate 

lute  alcohol  and  $  normal  NaOH 

added  to  it 

Sodium 

Elaldic    acid    dissolved    in    warm 

304 

3.8 

1250 

White  gel 

el  ai  date 

absolute   alcohol   and    i    normal 

NaOH  added  to  it 

Sodium 

Erucic  acid  dissolved  in  warm  abso- 

360 

12.6 

3500 

White  gel 

erucate 

lute  alcohol  and  }  normal  NaOH 

added  to  it 

56 


SOAPS  AND  PROTEINS 


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ij 

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THE  COLLOID-CHEMISTRY  OF  SOAPS 


57 


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58 


SOAPS  AND  PROTEINS 


TABLE  XIV 

GELATION  CAPACITIES  IN  cc.  PER  GRAM  OF  VARIOUS  SODIUM  SOAPS 
OF  THE  ACETIC  SERIES  WITH  BENZYL  ALCOHOL  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


Soap. 

Benzyl. 

Sodium  stearate  

110   (0  90) 

90   (  1    09) 

Sodium  myristate  

82  1    (1    19) 

Sodium  laurate 

75     (i   31) 

67}   (1    46) 

60     (1   64) 

40     (2  44) 

TABLE   XV 

GELATION  CAPACITIES  IN  cc.  PER  GRAM  OF  VARIOUS  SODIUM  SOAPS 
OF  THE  OLEIC  SERIES  WITH  BENZYL  ALCOHOL  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


Soap. 

Benzyl. 

Sodium  erucate  

30   (3   23) 

Sodium  oleate  .  .                           

50  (1   96) 

Sodium  elaidate 

20  (4  76) 

TABLE   XVI 

GELATION   CAPACITIES  IN  cc.  PER  GRAM   OF  VARIOUS   SODIUM   SOAPS  OF 
THE  ACETIC  SERIES  WITH  DIFFERENT  DIATOMIC  ALCOHOLS  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gei. 


Soap. 

Ethylene- 
glycol. 

Trimethylene- 
glycol. 

Sodium  stearate  
Sodium  palmitate 

80  (1.23) 
40  (2  44) 

250  (0.39) 
120  (0  83) 

Sodium  myristate  
Sodium  laurate  

10  (9.09) 

80  (1.23) 
40   (2.44) 
25   (3  84) 

Sodium  caprylate  
Sodium  caproate  



15  (6.25) 
10  (9  .09) 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


59 


TABLE   XVII 

GELATION   CAPACITIES   IN  cc.  PER   GRAM   OF   VARIOUS  SODIUM  SOAPS  OP 
THE  OLEIC  SERIES  WITH  DIFFERENT  DIATOMIC  ALCOHOLS  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


Soap. 

Ethylene- 
glycol. 

Trimethylene- 
glycol. 

Sodium  erucate  
Sodium  oleate  

30   (3.23) 

30  (3.23) 
60  (1   64) 

Sodium  elaidate.  .  . 

15  (6  25) 

TABLE   XVIII 

GELATION  CAPACITIES  IN  cc.  PER  GRAM  OF  VARIOUS  SODIUM  SOAPS 
OF  THE  ACETIC  SERIES  WITH  A  TRIATOMIC  ALCOHOL  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


Soap. 

Glycerin. 

Sodium  stearate  

150     (0.66) 

Sodium  palmitate 

50     (1   96) 

15      (6  25) 

8  (11   11) 

TABLE   XIX 

GELATION  CAPACITIES  IN  cc.  PER  GRAM  OF  VARIOUS  SODIUM  SOAPS  OF  THE 
OLEIC  SERIES  WITH  A  TRIATOMIC  ALCOHOL  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


Soap. 

Glycerin. 

Sodium  erucate  

30  (3.23) 
20  (4  76) 

18  (5  26) 

SOAPS  AND  PROTEINS 


IV 


THE  SYSTEM   SOAP/X.     COLLOID   SOAPS  IN   OTHER 
NON-AQUEOUS    "SOLVENTS" 

It  is  of  importance  for  the  theory  of  the  lyophilic  soap  colloids 
in  particular,  and  of  lyophilic  colloids  in  general,  to  see  how  much 


FIGURE  43. 


further  the  composition  of  these  systems  may  be  broadened  and 
still  yield  the  definitely  colloid  systems  under  discussion.  The 
soaps  form  admirable  materials  for  such  a  study,  for,  as  already 
observed,  they  yield  colloid  systems  not  only  with  water  and  the 
various  monatomic,  diatomic  and  triatomic  alcohols  but  also 
with  many  other  liquid  "  solvents." 

Some  colloid  systems  of  the  general  composition  soap/x  are 
illustrated  in  Fig.  43.     Here  sodium  stearate  and  sodium  oleate 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


are  seen  to  yield  gels  with  turpentine,  gasoline,  benzene,  toluene, 
chloroform  and  carbon  tetrachlorid.  The  list  of  "  solvents  " 
which  yield  such  results  can  be  further  lengthened  as  shown  in 
Figs.  44,  45  and  46  by  observing  that  meta-,  ortho-  and  para- 
xylene,  diethyl  and  butyl  ethers,  benzaldehyd  and  paraldehyd, 
turpentine,  limonene,  pinene,  gasoline,  heptane,  ethyl  cenan- 
thate,  amyl  acetate  and  triacetin  all  yield  satisfactory  results. 
The  experimental  details  covering  Fig.  43  a"re  contained  in  Table 
XX;  those  covering  Figs.  44,  45  and  46  in  Table  XXI.  It 


FIGURE  44. 

should  be  noted  that  the  gelation  capacities  of  Table  XX  are 
the  maximal  values;  in  the  rest  of  the  series  we  contented  our- 
selves with  the  mere  finding  that  lyophilic  colloid  systems  could 
be  produced  from  the  soaps  and  "  solvents  "  chosen  for  study. 

These  findings  indicate  that  a  large  variety  of  different  "  sol- 
vents "  may  all  yield  lyophilic  colloid  systems,  even  though  there 
is  little  chemical  relationship  between  the  members  of  the  various 
groups  studied.  What  this  means  for  the  general  theory  of  the 
lyophilic  colloid  state  is  now  to  be  discussed. 


SOAPS  AND  PROTEINS 


FIGUEE  45. 


FIGURE  46. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


TABLE   XX 

GELATION  CAPACITIES  IN  cc.  PER  GRAM  OF  VARIOUS  SODIUM  SOAPS 
WITH  DIFFERENT  NON- AQUEOUS  SOLVENTS  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


Soap. 

Turpentine. 

Gasoline. 

Benzene. 

Toluene. 

Chloroform. 

Carbon 
tetrachlorid. 

Sodium  stearate 
Sodium  oleate.  . 

3.8  (20.8) 
3.0  (25.0) 

3.2  (23.8) 
4.0  (20.0) 

3.0  (25.0) 
3.0  (25.0) 

6.0  (14.3) 
3.0  (25.0) 

3.6  (21.8) 
3.6  (21.8) 

6.4  (13.5) 
5.0  (16.7) 

TABLE   XXI 

GELATION  CAPACITIES  (Nor  MAXIMAL)  IN  cc.  PER  GRAM  OF  SODIUM 
STEARATE  WITH  DIFFERENT  NON-AQUEOUS  SOLVENTS  AT  18°  C. 

Values  in  parentheses  indicate  percent  of  soap  in  the  gel. 


*Af-xylene  
*O-xylene  

4.0  (20.0) 
4.0  (20.0) 

*P-xylene 

4  0  (20  0) 

Diethyl  ether  

2.0  (33.3) 

*Butyl  ether  

4.0  (20.0) 

*Benzaldehyd  

4.0  (20.0) 

*Paraldehyd 

4.0  (20  0) 

Turpentine 

3.0  (25.0) 

*Limonene 

4.0  (20.0) 

*Pinene                               

4.0  (20.0) 

Gasoline                       

3.0  (25.0) 

*Heptane                   

4.0  (20.0) 

*Ethyl  oenanthate 

4  0  (20  0) 

*Amyl  acetate  

4.0  (20.0) 

4.0  (20.0) 

*Because  of  the  slight  "solubility"  of  the  soaps  in  these  solvents  at  the  temperature  of 
a  boiling  water  bath,  this  was  increased  through  addition  of  a  small,  measured  volume 
of  methyl  alcohol  which  was  then  completely  evaporated  from  the  mixture  before  th« 
system  was  cooled  to  18°  C. 


64  SOAPS  AND  PROTEINS 


ON  THE  GENERAL  THEORY  OF  THE  LYOPHILIC  COLLOIDS 

1.  Historical  and  Critical  Remarks 

The  experiments  detailed  above  on  soap/water,  soap/alcohol 
and  soap/2  systems  help,  we  think,  towards  a  better  understand- 
ing of  a  number  of  technological,  physico-chemical  and  biological 
problems.  We  wish  first  to  comment  upon  their  value  for  a 
closer  definition  of  the  terms  hydrophilic  or  lyophilic  colloid.1  In 
spite  of  the  fact  that  we  now  recognize  the  existence  of  material 
in  the  colloid  state  and  utilize  its  many  important  properties 
for  the  solution  of  technological  or  scientific  phenomena,  it  is 
nevertheless  true  that  an  entirely  satisfactory  or  complete  defini- 
tion of  what  constitutes  the  colloid  state  is  not  yet  at  hand. 

Perhaps  the  best  established  and  most  universal  character- 
ization of  the  colloids  is  that  which  defines  them  as  diphasic  or 
polyphasic  systems  in  which  one  material  is  subdivided  into  a 
second  with  the  degree  of  subdivision  coarser  than  molecular 
and  not  so  coarse  as  to  fall  within  the  limits  of  microscopic  visi- 
bility. From  the  three  states  of  matter,  gaseous,  liquid  and 
solid,  it  is  obvious,  as  first  clearly  developed  by  WOLFGANG 
OsTWALD,2  that  nine  combinations  consisting  of  the  colloid  dis- 
persion of  any  one  of  these  materials  in  any  second  are  possible. 
These  may  be  tabulated  as  follows: 

gat  in  gas  liquid  in  gas       (steam)  solid  in  gas       (smoke) 

gas  in  liquid  (charged 


water) 
gas  in  solid     (meerschaum) 


liquid  in  liquid  (fine  emul-      solid  in  liquid  (metallic  gold  in 

sion)  water) 

liquid  in  solid   (opal)  solid  in  solid     (gold  ruby  glass) 


Of  the  nine  possible  combinations  eight  have  been  realized  (the 
colloid  dispersion  of  one  gas  in  a  second  being  impossible). 

1  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Science,  48,  143  (1918); 
ibid.,  49,  615  (1919);  Chem.  Engineer,  27,  184  (1919). 

2  WOLFGANG  OSTWALD:  Kolloid-Zeitschr.,  1,  291,  331  (1907);  Theoretical 
and  Applied  Colloid  Chemistry,  translated  by  MARTIN  H.  FISCHER,  42,  New 
York  (1917);    Handbook  of  Colloid  Chemistry,  2nd  English  Ed.,  translated 
by  MARTIN  H.  FISCHER,  43,  49,  Philadelphia  (1918). 


THE  COLLOID-CHEMISTRY  OF  SOAPS  65 

Of  these  dispersoids,  the  ones  of  greatest  interest  in  con- 
nection with  the  behavior  of  the  soaps  are  those  embraced  within 
the  heavy  black  square,  in  other  words,  those  which  have  the 
composition  liquid  plus  liquid  or  liquid  plus  solid.  According 
to  OSTWALD,  the  former  are  the  emulsion  colloids,  the  latter  the 
suspension  colloids;  or,  to  adopt  the  terminology  of  P.  P.  VON 
WEIMARN,  they  are  the  emulsoids  and  the  suspensoids. 

The  attempt  has  been  made  to  correlate  the  physical  properties 
of  each  of  these  systems  with  the  fact  that  the  two  phases  have, 
in  the  first  instance,  a  liquid  plus  liquid  composition,  or,  in  the 
second,  a  liquid  plus  solid  composition.  In  the  group  of  the 
first  are  found  many  of  the  "  viscous,  gelatinizing  and  not  readily 
coagulable  "  "  colloid  solutions  "  of  A.  A.  NoYES,1  or  the  hydro- 
philic  or  lyophilic  colloids  of  J.  PERRiN2  and  H.  FREUNDLICH  ;3 
in  the  second  are  the  "  non-viscous,  non-gelatinizing,  readily 
coagulable  "  "  colloid  suspensions  "  of  NOTES  or  the  hydrophobic 
or  lyophobic  colloids  of  PERRIN  and  FREUNDLICH.  The  cor- 
relation between  the  physical  state  of  the  phases  and  the  prop- 
erties of  the  mixed  systems  is  not  enough,  however,  to  characterize 
them  completely.  Liquid  mercury  in  water  for  example  yields 
only  a  suspension  colloid,  and  the  same  is  true  of  (liquid)  oil  in 
water;  on  the  other  hand,  (solid)  ferric  hydroxid,  generally  ranked 
among  the  suspension  colloids,  has  distinctly  hydrophilic  proper- 
ties in  high  concentration- in  water. 

Such  weaknesses  in  the  attempts  to  make  the  term  lyophilic 
colloid  synonymous  with  emulsion  colloid  and  lyophobic  colloid 
with  suspension  colloid  were  recognized  by  WOLFGANG  OSTWALD  4 
himself,  and  in  consequence  the  effort  was  made  by  him  to 
overcome  such  objection  by  declaring  the  lyophilic  colloids 
"  colloids  of  a  higher  order."  Specifically  he  assumed  that 
emulsion  colloids  were  not  "  merely  "  subdivisions  of  one  liquid 
in  a  second,  but  that  each  of  the  liquid  phases  was  itself  a  dis- 
persoid.  We  shall  see  below  that  this  view  is  correct. 

It  seems  to  us  that  the  characteristic  difference  between  lyophilic 
and  lyophobic  colloids  is  not  to  be  sought  in  their  liquid  plus  liquid 
or  liquid  plus  solid  character  but  in  the  fact  that  the  phases  are  either 

1  A.  A.  NOYES:  Jour.  Am.  Chem.  Soc.,  27,  85  (1905). 

2  J.  PERRIN:  Journal  de  Chimie  physique,  3,  84  (1905). 

3H.  FREUNDLICH:  Kolloid-Zeitschr.,  3,  80  (1908);  Kapillarchemie,  309, 
Leipzig  (1909). 

4  WOLFGANG  OSTWALP:  Kpllpid-Zeitschr.,  11,  230  (1912). 


66  SOAPS  AND  PROTEINS 

mutually  soluble  or  not.  (Liquid)  water  and  (liquid)  oil  yield 
only  lyophobic  colloids  (suspension  colloids  in  the  old  ter- 
minology) because  the  two  phases  are  mutually  insoluble,  but 
(liquid)  water  and  soap  (whether  liquid  or  solid)  yield  lyophilic 
colloids  (emulsion  colloids  in  the  old  terminology)  because  their 
mutual  solubility  is  high. 

The  importance  of  mutual  solubility  for  the  understanding 
of  some  of  the  phenomena  characteristic  of  colloids  was  drawn 
upon  some  years  ago  by  W.  B.  HARDY.1  HARDY  used  the  concept 
of  mutual  solution  to  explain  the  physical  phenomena  encountered 
in  the  gelation  of  protein-water-salt  mixtures,  but  owing  to  the 
objection  that  the  phases  did  not  show  the  constant  chemical 
composition  demanded  by  theory,  this  important  idea  seems  to 
have  been  largely  dropped.  For  reasons  which  become  apparent 
as  we  proceed,  this  objection  is  not  valid,  and  it  seems  possible 
to  make  a  fairly  inclusive  analysis  of  what  we  mean  by  hydro- 
philic  colloids  and  the  changes  in  their  states,  as  soon  as  we  add 
to  the  concepts  of  mutual  dispersion  in  degrees  coarser  than 
molecular  and  mutual  solubility  of  the  phases  a  third  important 
point,  namely,  that  of  the  enormous  increase  in  viscosity  observed 
whenever  two  liquids  or  a  liquid  and  a  solid,  themselves  possessed 
of  low  viscosity,  are  subdivided  into  each  other. 

To  make  the  last  of  these  points  clear,  it  is  only  necessary 
to  introduce  the  example  of  WOLFGANG  OSTWALD,  of  water  and 
dry  sand,  and  the  observations  of  J.  FRIEDLANDER  and  V.  ROTH- 
MUND  on  the  viscosity  of  mutually  soluble  liquids  in  the  zone 
of  their  critical  temperature.  While  dry  sand  "  runs  "  easily 
and  the  viscosity  of  pure  water  is  relatively  low,  wet  sand  may 
be  readily  molded  and  hold  its  shape.  The  example  of  the  mutu- 
ally soluble  system  phenol/water  (which  is  considered  particularly 
apt  in  the  matter  of  understanding  the  colloid  behavior  of  soap/ 
water  systems)  is  shown  in  Fig.  47.  The  bottle  on  the  extreme 
left  contains  only  phenol  (which  at  18°  C.  is  a  crystalline  mass 
like  any  "  pure  "  soap  at  a  proper  temperature).  The  succeed- 
ing bottles  contain  the  same  weight  of  phenol,  plus  gradually 
increasing  amounts  of  water.  As  more  and  more  water  is  added 
the  phenol  fails  to  crystallize;  up  to  and  including  the  sixth  bottle 
from  the  left,  only  "  solutions  "  are  obtained,  but  these  are  solu- 

1  W.  B.  HARDY:  Jour.  Physioi.,  24,  158  (1899);  Zeitschr.  f.  physik.  Chem., 
88,  326  (1900). 


THE  COLLOID-CHEMISTRY  OF  SOAPS'    -'- 


.,63  SOAPS  AND  PROTEINS 

tions  of  water  in  phenol.  The  seventh  bottle  shows  two  layers — 
below,  one  of  phenol  saturated  with  water;  above,  a  solution  of 
phenol  in  water.  With  further  additions  of  water  the  latter  type 
of  solution  grows  at  the  expense  of  the  former,  until  finally,  in 
the  bottle  second  from  the  extreme  right  of  the  series  nothing 
but  a  solution  of  phenol  in  water  remains.1 

Of  importance  for  our  further  discussion  is,  first,  the  existence 
of  the  two  types  of  solution,  that  of  water-in-phenol  and  that  of 
phenol-in-water.  The  physical  constants  of  these  two  solutions 
are  totally  different  and  they  behave  differently,  too,  toward 
changes  in  external  conditions  like  temperature  or  the  effects 
of  added  substances  (acids,  bases,  salts,  indicators,  etc.).  A 
second  point  of  importance  is  the  behavior  of  such  a  system  as 
is  represented  in  the  fourth  or  fifth  bottle  from  the  right  when 
subjected  to  increases  or  decreases  in  temperature.  When  the 
temperature  is  raised  the  watered -phenol  phase  goes  over  and  into 
solution  in  the  phenolated-water  phase.  It  is  characteristic  of 
liquids,  when  their  temperature  is  being  lowered,  to  show  a  pro- 
gressive increase  in  viscosity.  The  warmed  solution  of  phenol- 
in-water  also  shows  such  a  progressive  increase  in  viscosity  as 
its  temperature  is  lowered,  but,  as  first  noted  by  FRIEDLANDER 
and  ROTHMPND,  this  progressive  increase  shows  a  sharp  break 
upon  reaching  the  critical  temperature,  at  which  the  phenol 
begins  to  separate  out. 

This  break  expresses  itself  as  a  sharp  rise  in  viscosity,  which 
increases  for  a  time  and  then  falls  off  again,  so  that  with  further 
lowering  of  temperature  a  viscosity  curve  more  like  the  original 
"  normal  "  is  again  obtained. 

We  are  indebted  to  WOLFGANG  OSTWALD  for  pointing  out 
that,  in  this  critical  zone  during  which  the  phenol/water  system 
is  opalescent,  we  are  in  reality  dealing  with  a  colloid  system  (con- 
sisting of  watered-phenol  dispersed  in  phenolated-water). 

1  In  analogy  to  what  happens  in  the  "salting-out"  of -soaps,  which  is  the 
subject  of  Section  X  (page  93),  it  is  well  to  explain  the  nature  of  the  con- 
tents of  this  right-hand  bottle  in  the  series.  This  was  originally  nothing  but 
a  solution  of  phenol  in  water,  but  through  the  addition  of  ordinary  table  salt 
the  phenol  was  "salted  out"  so  that  now  a  phenol  phase  with  some  water 
dissolved  in  it  (analogous  to  the  salted-out  soap  of  the  manufacturer)  is  seen 
floating  at  the  surface  of  the  liquid  in  the  bottle. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  69 

2.  On  the  Theory  of  Soap  Gels 

It  is  our  purpose  now  to  show  that  the  behavior  of  the  soap/water, 
soap/alcohol  and  soap/x  systems  previously  discussed  is  also  best 
understood  in  the  terms  of  the  submolecular  dispersion  into  each 
other  of  two  materials  possessed  of  a  fair  degree  of  mutual  solubility.1 

When  one  tries  to  state  in  the  simplest  possible  terms  what  it 
is  that  happens  when  a  definite  mixture  of  soap  with  some  solvent 
(like  soap  and  water),  which  at  the  temperature  of  boiling  water 
is  a  mobile  liquid,  is  seen  to  set  into  a  dry,  solid  mass  as  its  temp- 
erature is  reduced,  it  seems  easiest  to  think  of  the  whole  as  a 
change  from  what  is,  at  the  higher  temperature,  essentially  a 
solution  of  soap  in  water  to  that  which  is,  at  the  lower  temperature, 
a  solution  of  water  in  soap.  Between  these  extremes  and  as 
determined  by  the  temperature  and  by  the  relative  concentra- 
tions of  soap  and  of  water,  we  get  various  mixtures  of  solvated- 
soap  in  soap-water  or  of  soap-water  in  solvated-soap.  The  situa- 
tion in  the  case  of  the  soaps  in  the  presence  of  limited  volumes  of 
water  is  identical,  in  other  words,  with  the  changes  which  may 
be  seen  in  mutually  soluble  systems  of  the  type  phenol/water, 
ether/water  or  protein/water  as  studied  by  J.  FRIEDLANDER, 
V.  ROTHMUND,  W.  B.  HARDY  and  their  various  followers. 

Turning  first  to  a  study  of  the  mechanism  employed  for  the 
production  of  these  colloid  soap  systems,  it  is  evident  that  they 
are  formed  for  the  most  part  by  "  dissolving  "  a  unit  weight  of 
soap  in  a  definite  volume  of  water  at  a  rather  high  temperature. 
In  the  accepted  parlance,  it  may  be  said  that  through  increase  in 
temperature  the  solubility  of  the  soap  in  the  water  is  tremen- 
dously increased.  While  the  lower  soaps  of  the  acetic  acid  series 
are  readily  soluble  in  water  (even  at  relatively  low  temperatures), 
the  upper  members  behave  like  the  lower  members  if  the  tempera- 
ture is  raised.  The  soap  goes  into  solution  in  the  water.  The 
truth  of  this  assertion  is  indicated  by  the  available  physico- 

1  We  are  not  unaware  that  the  concept  "solution"  needs  itself  to  be  defined. 
While  the  field  of  "solution"  constitutes  slippery  ground,  we  accept,  for 
pragmatic  reasons,  as  characteristic  of  the  "true"  solution,  the  teachings  of 
WOLFGANG  OSTWALD  and  P.  P.  VON  WEIMARN,  who  define  such  solutions  as 
dispersions  of  A  in  B  with  the  degree  of  subdivision  measurable  in  molecular 
or  smaller  values.  To  express  the  matter  in  the  terms  of  A.  P.  MATHEWS, 
we  may  say  that  A  is  dissolved  in  B  or  vice  versa  when  the  solvent  has  over- 
come the  cohesive  forces  of  the  dissolved  substances.  As  MATHEWS  has 
shown,  the  forces  of  cohesion  operate  within  molecular  dimensions. 


70 


SOAPS  AND  PROTEINS 


chemical  observa- 
tions which  show 
that  the  lower  soaps 
behave  "  normally  " 
even  at  relatively 
low  temperatures; 
but  all  the  soaps, 
even  the  higher  ones, 
tend  to  behave  os- 
motically,  electric- 
ally, optically,  etc., 
as  so-called  "  true  " 
solutions  when  their 
temperature  is  suffi- 
ciently  raised 
(KRAFFT). 

To  illustrate  the 
matter  in  crude 
fashion  and  more 
particularly  for  any 
of  the  higher  soaps 
(which  experiment 
has  shown  to  be 
particularly  favor- 
able for  the  produc- 
tion of  "  colloids  ") 
and  to  illustrate  the 
effects  of  a  lowering 
of  temperature,  Figs. 
48  and  49  are  intro- 
duced. Fig.  48  shows 
the  results  if  the 
separating  phase  has 
a  liquid  character; 
Fig.  49,  if  it  is  solid 
or  crystalline.  The 
diagrams  are  sup- 
posed to  show  the 
results  when  two 
mutually  soluble 


SOAP  IN  WATER 


WATER  IN   SOAP 


FIGURE  48. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


71 


SOAP  IN  WATER 


B 


************** 
************** 

*  *  *  *  *  *  *  *  *  *  *  *  % 


************** 

*********%%i*%* 

**"  3$ 
•*-* 


%'iR^  ^ 


u 


iftffi 


»ff,^!|>S 

,.^..5Vi^,»^  -;^'.-S 


w 


WATER  IN   SOAP 

FIGURE  49. 


substances,  like  A 
and  B,  (water  and 
soap,  or  alcohol  and 
soap)  are  mixed  to- 
gether. When  B  (or 
the  soap)  is  readily 
soluble  in  A  and  the 
concentration  is  right- 
ly chosen,  there  results 
a  true  solution  at  the 
higher  temperature. 
This  matter  is  repre- 
sented by  the  region 
marked  A  in  the  dia- 
grams (the  soap  is 
dispersed  molecularly 
or  ionically  in  the 
solvent).  The  lower- 
most members  of  the 
fatty  acid  series  form 
systems  of  this  type 
only,  even  at  relative- 
ly low  temperatures, 
but  the  members 
higher  in  the  series 
form  such  systems 
only  at  the  higher 
temperatures.  The 
soap  manufacturer 
who  makes  his  prod- 
uct by  "  boiling," 
in  essence  makes  his 
soaps  in  such  true 
solution. 

What  happens  now 
when  the  temperature 
is  lowered?  The  solu- 
bility of  the  soap  in 
the  water  is  obvious- 
ly decreased.  As  the 


72  SOAPS  AND  PROTEINS 

saturation  point  is  attained,  the  soap  particles  assume  not  only 
molecular  size  but  more  than  molecular  size.  By  definition, 
therefore,  we  approach  with  falling  temperature  the  realm  of  the 
colloids,  or  that  of  dispersions  of  one  material  in  a  second  with  the 
degree  of  dispersion  showing  dimensions  greater  than  molecular. 
The  gradual  increase  in  the  size  of  the  soap  particles  (or  increase 
in  their  number)  with  lowering  of  the  temperature  is  represented 
by  the  regions.  B,  C,  D,  E  and  F  in  the  two  diagrams. 

Thus  far  we  have  explained  merely  the  production  of  a  colloid 
system  by  the  ordinary  process  of  bringing  about  supersaturation 
and  an  agglomeration  of  particles  previously  more  highly  dis- 
persed. It  is  obvious  that  such  agglomeration  may  yield  either 
a  lyophobic  (or  so-called  suspension  colloid)  or  a  lyophilic  (or 
so-called  emulsion  colloid).  The  lyophobic  colloid  results  when  the 
solvent  is  not  soluble  in  the  precipitating  phase;  the  lyophilic  colloid 
when  the  solvent  is  soluble  in  the  precipitating  phase.  When  soap 
falls  out  of  solution  from  such  a  solvent  as  allyl  alcohol  the  former 
of  these  possibilities  is  realized;  when  it  falls  out  in  water,  alcohol, 
toluene,  benzene,  etc.,  the  latter  is  realized.  The  black  circles  in 
the  diagram  of  Fig.  48  or  the  black  crystal  masses  in  Fig.  49 
represent  more  therefore  in  the  latter  instance  than  a  mere  pre- 
cipitate of  pure  soap;  they  are  this,  plus  a  certain  amount  of  the 
water,  alcohol  or  other  "  solvent  "  dissolved  in  them.1 

At  a  sufficiently  low  temperature  the  soap  aggregates  will  have 
become  so  large  or  so  numerous  as  to  touch  and  coalesce.  If  this 
process  continues  to  a  sufficient  extent  the  system  will  ultimately 
represent,  in  essence,  nothing  but  soap  in  which  the  previous 
"  solvent "  has  been  dissolved.  This  situation  is  represented 
diagram matically  by  the  zone  Z  of  Figs.  48  and  49. 

A  study  of  Figs.  48  and  49  shows,  however,  that  between  the 
upper  extreme  (A)  of  a  solution  of  the  soap  in  the  solvent  and  the 

1  We  do  not  here  distinguish  between  such  "dissolved"  water  and  water 
of  crystallization.  Obviously  both  values  are  included.  While  we  have  no 
desire  to  trespass  upon  the  fields  of  theoretical  chemistry  we  feel  strongly 
compelled  to  the  view  that  "solution"  always  means  (chemical)  union  between 
solvent  and  dissolved  substance.  In  the  "dilute"  solutions  this  effect  is 
largely  lost  sight  of,  however,  because  of  the  large  overplus  of  the  pure 
"solvent,"  the  properties  of  which  then  continue  to  dominate  the  whole 
system.  The  union  between  solvent  and  any  substance  X  need  not,  more- 
over, be  of  one  kind  only.  When  phenol  dissolves  in  water  one  type  of  union 
between  the  two  is  accomplished;  when  water  dissolves  in  phenol  the  combi- 
nation is  a  totally  different  one. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  73 

lower  extreme  (Z)  of  a  solution  of  the  solvent  in  the  soap,  there 
exist  two  main  zones  of  mixed  systems,  one  below  the  upper  (B, 
C,  D  and  E)  consisting  of  a  dispersion  of  solvated-soap  in  the 
soaped-solvent,  and  a  second  above  the  lower  (Y,  X,  W  and  V) 
consisting  of  soaped-solvent  in  the  solvated-soap.  These  two 
mixed  systems  are  in  essence  "  emulsions  "  (if  both  phases  are 
liquid)  or  "  suspensions  "  (if  at  least  one  phase  is  solid)  but  of 
opposite  types;  and  as  such  (even  when  of  the  same  quantitative 
chemical  constitution)  are  possessed  of  totally  different  physical 
properties.  The  former  corresponds,  for  example,  to  an  emulsion 
of  oil-in-water  or  a  suspension  of  quartz-in-water;  the  second  to 
an  emulsion  of  water-in-oil  or  a  system  of  water-in-quartz.  And 
as  the  former  (as  illustrated  by  milk)  will  mix  with  water,  wet 
paper  and  show  a  certain  viscosity  value,  the  latter  (as  illustrated 
by  butter)  will  mix  only  with  oil,  will  grease  paper  and  show  an 
entirely  different  viscosity.1 

Returning  to  the  lyophilic  soaps  and  the  diagram,  it  is  obvious 
that  as  we  descend,  with  lowering  of  temperature,  from  the  region 
A,  we  pass,  in  the  regions  B,  C  and  D,  through  increasingly  viscid 
liquid  colloid  "  solutions,"  but  all  of  them  emulsions  or  suspen- 
sions of  the  type  solvated-soap  in  soaped-solvent.  In  the  region 
E,  the  particles  of  solvated  soap  almost  touch,  and  here  the  highest 
(liquid)  viscosity  is  obtained.  In  F  they  do  touch  and  now  form 
a  continuous  external  phase.  At  this  point  we  change  to  the 
opposite  type  of  emulsion  or  suspension — the  previously  liquid 
colloid  becomes  solid,  or,  as  we  say,  it  gels.  As  we  shall  show 
later2  the  two  types  of  system  not  only  have  different  physical 
constants  but  behave  differently  toward  such  added  materials  as 
indicators. 

1  See  in  this  connection   MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER 
Science,  43,  468  (1916);  MARTIN  H.  FISCHER:  Fats  and  Fatty  Degeneration, 
20,  New  York  (1917). 

2  See  page  77;    also    MARTIN    H.  FISCHER:    Science,  49,  615   (1919); 
Chem.  Engineer,  27,  271  (1919). 


74  SOAPS  AND  PROTEINS 


VI 

DEFINITION  OF  HYSTERESIS,  SWELLING,  LIQUEFACTION, 
GELATION  CAPACITY,  SOLVATION  CAPACITY,  SYNERE- 
SIS,  SOL 

We  should  now  like  to  emphasize  how  this  concept  of  the 
changes  which  the  soaps  suffer  in  passing  from  liquid  sols  to  dry 
gels  may  help  to  explain  a  number  of  the  "  strange  "  character- 
istics of  colloid  systems. 

1.  A  first  question  under  this  heading  is  that  of  the  nature 
of  hysteresis,  more  particularly  that  observed  when  a  colloid  is 
subjected  to  changes  in  temperature.  The  importance  of  the 
thermal  history  of  a  colloid  system  is  constantly  stressed.  It 
is  generally  true  of  the  lyophilic  colloids  that  when  subjected 
to  heat  manipulation  they  tend  to  hold  fast  to  the  characteristics 
of  their  previous  states.  A  colloid  on  cooling,  for  example,  first 
sets  at  a  certain  temperature;  yet  the  same  colloid  after  setting, 
fails  on  reheating  to  liquefy  at  this  temperature — it  usually 
first  "  melts  "  at  a  higher  one.  In  fact  it  may  be  said  quite 
generally  that  the  curve  showing  the  increase  in  viscosity  of  a 
lyophilic  colloid  with  lowering  of  temperature  is  rarely  identical 
with  that  portraying  the  decrease  in  viscosity  when  the  temper- 
ature is  raised  through  the  same  range.  If  the  fact  is  remembered 
that  the  absolute  values  of  two  mutually  soluble  substances  are 
rarely  the  same,  and  that  the  rates  at  which  they  go  into  solution 
in  each  other  are  usually  different,  many  of  these  difficulties 
disappear.  Figs.  48  and  49  show  diagrammatically  not  only 
what  happens  when  the  temperature  of  a  solution  of  soap  in  some 
solvent  is  lowered  but  also,  in  the  lower  halves  of  the  pictures, 
the  effects  of  warming  a  gel.  Increasing  the  temperature  of  the 
original  solvated-soap  shown  in  region  Z  increases  the  solubility 
of  the  soap  in  the  water,  and  so  the  colloid  dispersion  Y  results, 
consisting  of  soaped-solvent  in  solvated-soap.  Further  increase 
in  temperature  yields  the  regions  X  and  W,  but,  because  of  the 
persistence  of  the  solvated-soap  as  the  external  phase,  all  these 
regions  continue  to  show  a  rigidity  or  viscosity  higher  than  that 
of  systems  of  the  same  quantitative  composition  produced  by 


THE  COLLOID-CHEMISTRY  OF  SOAPS  75 

a  lowering  of  temperature  from  a  higher  level.  The  gel  first 
shows  signs  of  liquefaction  where  the  soaped-solvent  particles 
begin  to  touch  and  thus  to  form  the  external  phase,  as  in  the 
regions  V  or  U.  It  is  for  these  reasons  that  the  region  of  greatest 
ambiguity  and  of  greatest  hysteresis  is  found  in  the  broken  middle 
portions  of  the  diagram  (D,  E,  F  and  W,  V,  U).  Just  as  long 
periods  of  time  are  required  to  make  solution  phenomena  attain 
their  final  values,  just  so  must  mutually  soluble  systems  subjected 
to  changes  in  their  environment  be  expected  to  come  only  slowly 
into  a  state  of  their  final  equilibrium. 

2.  Some  years  ago  we  showed,  in  the  case  of  gelatin,1  that 
the  "  swelling  "  of  this  substance  and  its  liquefaction  are  not 
identical  processes  and  that  the  latter  is  not  a  mere  continuation 
of  the  former.  When  ordinary  gelatin  is  thrown  into  water, 
it  swells  up  somewhat,  but  the  amount  of  this  swelling  is  enor- 
mously increased  if  a  little  acid  is  added  to  the  water.  If  lique- 
faction were  a  mere  continuation  of  this  swelling,  then  the  addition 
of  a  little  acid  to  a  gelatin  near  its  gelation  point  ought  to  make 
it  set.  As  a  matter  of  fact,  not  only  does  this  not  happen,  but 
the  addition  of  such  acid  to  a  previously  solid  gelatin  makes  it 
liquefy.  As  maintained  at  that  time,  an  increased  "  swelling  " 
was  declared  to  be  an  increased  capacity  for  taking  up  the  solvent; 
an  increased  tendency  to  liquefy,  the  expression  of  an  increase 
in  the  degree  of  dispersion  of  the  colloid  material. 

The  concept  of  the  lyophilic  colloid  as  here  developed  now 
permits  us  to  state  more  clearly  just  what  each  of  these  views 
embraces.  Increased  swelling  due  to  increase  in  hydration  or 
solvation  capacity  means  increased  solubility  of  the  solvent  in 
the  dispersed  substance.  When  acid  is  added  to  gelatin  (thus 
forming  an  acid  gelatinate)  water  is  more  soluble  in  the  newly 
formed  material  than  in  the  neutral  gelatin.  Acid  is  therefore 
said  to  increase  the  swelling  of  protein.  But  an  acid  proteinate  is 
also  more  soluble  in  water  than  is  the  neutral  protein.  If  the 
concentration  of  the  system  is  properly  chosen,  the  addition  of 
acid  will  therefore  make  a  gelatin/water  system,  solid  by  itself, 
tend  to  remain  "  in  solution  "  or,  as  more  generally  stated,  the 
gelatin  fails  to  "set."  Expressed  the  other  way  about,  the  presence 

1  MARTIN  H.  FISCHER:  Science,  42,  223  (1915);  MARTIN  H.  FISCHER 
and  MARIAN  O.  HOOKER:  ibid.,  46,  189  (1917);  Jour.  Am.  Chem.  Soc.,  40, 
272  (1918);  ibid.,  40,  292  (1918);  ibid.,  40,  303  (1918). 


76  SOAPS  AND  PROTEINS 

of  acid  makes  the  gelatin  "  liquefy"  or  "  go  into  solution."  Using 
Figs.  48  and  49  to  illustrate  what  has  been  said,  the  addition  of 
acid  to  a  previously  solid  gelatin  moves  the  whole  system  from 
some  such  lower  region  as  Z,  Y,  X,  or  W  into  one  of  the  upper 
zones  like  V  or  U. 

3.  Throughout   the   experiments   described   in   the   previous 
sections  we  have  used  the  formation  of  a  dry  gel  as  the  measure 
of  the  "  gelation  capacity  "  of  a  colloid.     We  may  now  attempt 
to  say  just  what  this  means.     It  obviously  includes  more  than 
the  term  salvation  capacity.     The  latter  measures  the  solubility 
of  the  solvent  in  the  colloid  material  and  is  synonymous  with  the 
swelling   capacity.     Gelation,    however,   includes   not   only   this 
value  but  more — namely,  everything  embraced  within  the  region 
of  the  emulsification  or  enmeshing  of  a  "  solution  "  of  the  colloid 
material  in  the  solvent,  within  the  solvated  colloid  as  an  external 
"  dry  "  phase.     It  embraces  everything  in  Figs.  48  and  49  up 
to  and  including  the  zone  V. 

4.  Just  above  this  region  it  is  apparent  that  the  more  solid 
phase  may  no  longer  be  adequate  to  enclose  all  the  "  solution  " 
of  colloid  in  solvent.     When  this  upper  region  is  reached  the 
colloid  system  tends  to  "  sweat  " — or  to  use  the  term  of  THOMAS 
GRAHAM  the  gel  shows  "  syneresis."     We  may  still  have  before 
us  a  gel,  but  it  is  now  no  longer  "  dry." 

When  the  dispersion  of  a  liquid  in  an  enveloping  phase  which 
is  also  a  liquid  is  compared  with  the  dispersion  of  a  liquid  in  a 
more  solid  (crystalline)  phase,  (as  indicated  in  the  zones  V  of 
Figs.  48  and  49)  it  is  clear  that  the  tendency  to . "  leak  "  the 
liquid  phase  is  greater  and  is  more  likely  to  occur  early  in  the 
case  of  the  latter  system  than  in  the  former.  It  is  for  this 
reason  that  the  more  "  solid  "  gels  regularly  show  earlier  and 
greater  syneresis  than  the  more  "  elastic  "  or  "  liquid  "  gels. 

To  go  sufficiently  above  the  region  U  is  to  be  in  the  regions 
E  and  D.  We  now  no  longer  say  that  there  is  syneresis  or  that 
this  has  become  excessive  but  we  say  that  the  gel  has  gone  into 
or  persists  in  the  "sol"  state. 

5.  As  a  final  word  we  should  like  to  emphasize  the  fact  that  the 
concept  of  the  lyophilic  colloid  as  outlined  here  sets  no  limitations  upon 
the   nature  of  the   materials  that  may  make  up  such  a  system  and 
makes  no  specifications  as  to  the  nature  of  the  forces  which  guarantee 
the  stability  of  the  colloid  system.    They  are  in  general  any  or  all 


THE  COLLOID-CHEMISTRY  OF  SOAPS  77 

the  forces  which  appear  in  or  are  operative  in  solutions  of  the 
most  varied  kinds.  This  is  emphasized  because  there  has  been 
much  written,  for  example,  regarding  the  all-important  effects 
of  the  electrical  charges  in  determining  the  stability  of  colloids 
in  general  and  of  the  lyophilic  colloids  in  particular.  We  do 
not  wish  to  deny  the  importance  of  this  factor  in  some  colloid 
systems  or  under  certain  conditions,  but  it  is  too  narrow  a  view 
to  take  of  what  constitutes  the  lyophilic  colloids  in  general.  While 
the  play  of  electrical  forces  may  be  apparent  in  systems  composed ' 
of  soaps  and  water,  in  those  of  proteins  and  water,  etc.,  lyophilic 
colloid  systems  may  be  built  up,  as  illustrated  in  the  preced- 
ing pages,  of  materials  in  which  the  electrical  factors  are  either 
negligible  or  absent  entirely.  It  will  prove  somewhat  difficult, 
to  say  the  least,  to  conjure  up  orthodox  electrical  notions  in 
systems  containing  nothing  but  soaps  with  anhydrous  alcohol, 
toluene,  benzene,  chloroform  or  ether. 


VII 
ON  THE  REACTION   OF   SOAPS  TO   INDICATORS 

In  order  to  get  ground  materials  of  strictly  reproducible  type 
for  the  observations  on  soaps  detailed  in  the  preceding  pages, 
we  followed  the  expedient  of  producing  "  neutral "  soaps  by 
simply  adding  to  each  other  the  necessary  gram  equivalents  of 
highly  purified  fatty  acids  and  carefully  standardized  solutions 
of  alkali.  We  found  that  this  method  yielded  more  satisfactory 
results  than  that  of  others  who  tried  to  obtain  "  neutral,"  "  slightly 
alkaline  "  or  "  slightly  acid  "  soaps  by  adding  to  each  other  fatty 
acid  and  standard  alkali  until  some  chosen  indicator  was  pre- 
sumed to  show  the  mixture  neutral,  alkaline  or  acid.  As  the  next 
paragraphs  will  show,  such  indicator  methods  as  ordinarily 
employed  are  highly  fallacious.  As  a  matter  of  fact  the  errors 
incident  to  the  approach  to  the  problem  by  the  latter  method 
have  long  been  familiar  to  the  practical  soap  chemists,  for  they 
have  for  decades  past  determined  the  presence  of  "  free  alkali  " 
or  "  free  fatty  acid  "  in  their  soaps  by  indirect  methods.  The 
following  observations  not  only  show  how  unreliable  are  the 
commonly  employed  indicator  methods  but  why  they  must  be  so, 


78  SOAPS  AND  PROTEINS 

not  only  in  the  specific  instance  of  the  different  soaps  but  in  all 
similar  colloid-chemical  systems  as  represented  by  the  most  varied 
types  of  chemical  reaction  encountered  in  technological  practice  and 
in  living  cells  under  physiological  and  pathological  circumstances.1 
Incidentally  they  also  bring  proof  for  the  theoretical  views  devel- 
oped above,  according  to  which  the  system,  soap-dissolved-in 
solvent  is  something  totally  different  from  the  system,  solvent- 
dissol  ved-in-soap . 


Our  fundamental  conclusion  may  be  stated  thus:  When  a 
11  neutral "  soap  has  been  produced  through  combination  of  the 
necessary  gram  equivalents  of  pure  fatty  acid  with  standard  alkali, 
it  is  either  acid,  neutral  or  alkaline  to  such  an  indicator  as  phenol- 
phthalein,  depending  upon  the  concentration  of  the  water  in  the 


For  purposes  of  illustration  we  may  choose  the  behavior  of  a 
rather  concentrated  solution  of  sodium  oleate,  as  one  made  by 
combining  one  mol  of  fatty  acid  with  one  liter  of  normal  sodium 
hydroxid  solution  (practically  a  molar  or  30  percent  "  solution  " 
of  the  soap  in  water).  Phenolphthalein  added  to  such  a  concen- 
trated sodium  oleate/water  system  remains  colorless,  as  shown 
in  the  lower  portions  of  the  test  tube  of  Fig.  50.  As  soon,  how- 
ever, as  water  is  added  to  this  colorless  mixture  it  begins  to  turn 
pink,  and,  with  increasing  dilution  of  the  soap,  becomes  bright 
red,  as  evidenced  in  the  upper  portion  of  the  tube  in  Fig.  50. 

What  has  been  said  of  sodium  oleate  is  true  in  general  of  all 
the  soaps  (excepting  such  very  low  members  as  the  formates, 
acetates,  etc.)  though  for  demonstration  purposes  the  higher 
fatty  acid  soaps  with  their  lower  solubility  in  water  are  better 
than  the  soaps  of  the  lowermost  members  in  any  fatty  acid  series. 
An  indicator  (like  phenolphthalein)  added  to  a  chemically  neutral 
sodium  palmitate  or  sodium  stearate/water  system  (either  a  solid 

1  It  may  be  well  to  emphasize  here  that  normal  cells  are  essentially  sys- 
tems of  water-dissolved-in-protein.  Indicators  are  therefore  trickiest  when 
applied  to  these  systems.  In  disease  the  affected  cells  suffer  changes  which 
often  are  in  the  direction  of  "true"  solution,  in  other  words,  the  cells  tend  to 
develop  into  systems  of  the  type,  protoplasm-dissolved-in-water.  Indicator 
methods  become  more  reliable  as  this  happens  but  only  for  those  portions  of 
the  cell  which  are  of  this  "true"  solution  type.  See  the  later  pages  of  this 
volume. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


79 


gel  or  a  liquid  mixture)  turns  the  liquid  portion  of  the  system  a 
bright  red  while  the  masses  of  soap  floating  in  this  liquid  remain 
pure  white. 

The  common  explanation  of  what  happens  in  these  instances 
is,  of  course,  that  of  the  physical  chemists,  who  assume  that  in 
the  concentrated  soap  "  solution  "  there  is  little  hydrolysis  of  the 
soap,   while   in   the   more   dilute   one   such 
hydrolysis  is  increased  and,  sodium  hydroxid 
being  a  stronger  alkali  than  oleic  acid  is  an 
acid,  an  indicator  at  once  betrays  the  excess 
of  hydroxyl  ions. 

Without  listing  the  objections  which  may 
be  raised  against  such  an  explanation 
(which  at  best  accounts  for  but  a  small  por- 
tion of  what  happens),  it  seems  necessary, 
in  order  to  get  a  more  satisfactory  interpre- 
tation of  the  whole  picture,  to  call  to  mind 
the  physical  constitution  of  the  lyophilic 
colloids  as  previously  discussed  in  these 
pages  and,  in  the  case  of  the  soaps,  to  dis- 
tinguish between  the  behavior  of  those  por- 
tions of  such  systems  which  have  the  com- 
position water-dissolved-in-soap  and  those 
which  have  the  composition  soap-dissolved- 
in-water.  The  two  are  totally  different, 
and,  while  indicator  methods  may  be  used 
in  an  attempt  to  analyze  the  latter,  they 
need  not  be  (and  are  not)  so  applicable  to 
the  former.  The  so-called  concentrated  soap 
"  solutions  "  are  essentially  solutions  of  the 
solvent  in  the  soap,  while  the  more  dilute  FIGURE  50 

ones  are  systems  of  the  opposite  type,  and 
physico-chemical  methods  and  the  laws  governing  dilute  solutions 
may  therefore  be  applied  only  to  the  latter. 

The  correctness  of  these  various  deductions  may  be  tested  by 
the  use  of  such  an  indicator  as  phenolphthalein  upon  solid  soap 
gels  which,  as  previously  emphasized,  represent  mixed  systems  of 
soap-water  in  (solid)  solvated-soap.  If  phenolphthalein  is  applied 
directly  to  a  fresh  section  of  sodium  stearate,  for  example,  the 
framework  of  the  gel  (in  other  words,  the  water-in-soap  portion 


80  SOAPS  AND  PROTEINS 

of  the  system)  remains  uncolored  while  the  contents  of  this  frame- 
work (the  soap-in-water  portion)  turns  bright  red.  A  drop  of 
phenolphthalein  solution  dropped  upon  a  10  percent  sodium 
stearate/water  gel  remains  uncolored.  If,  however,  the  gel  is 
slightly  squeezed  (which  breaks  the  encircling  hydrated  sodium 
stearate  film  and  squeezes  out  the  enclosed  solution  of  soap-in- 
water)  the  spot  turns  bright-red.  Any  other  solid  soap/water 
system  behaves  in  similar  fashion. 

Another  variant  of  the  experiment  may  be  made  by  warming 
a  concentrated  sodium  oleate  or  other  soap  solution  which  at 
ordinary  temperature  fails  to  color  to  phenolphthalein.  Such  a 
mixture,  on  being  warmed,  turns  pink.  While  it  is  ordinarily 
said  that  under  such  circumstances  the  hydrolysis  of  the  soap  is 
increased,  it  is  equally  true  that  such  a  temperature  change  marks 
a  displacement  in  the  system  from  a  solution  of  the  solvent  in  the 
soap  to  one  of  the  soap  in  the  solvent. 

To  make  sure,  for  experimental  purposes,  of  definitely  "  acid  " 
or  "  alkaline  "  soaps  we  have  added  to  our  chemically  "  neutral  " 
soaps  (like  molar  sodium  oleate)  known  and  large  surpluses  of  free 
fatty  acid  or  alkali.  When  free  fatty  acid  is  added  it  emulsifies 
readily  in  the  soap,  yielding  a  mixture  more  viscid  than  the  origi- 
nal soap  gel  and  practically  as  transparent  as  the  original  sodium 
oleate.  Phenolphthalein  added  to  the  mixture  remains  colorless. 
Still,  when  water  is  added  to  such  an  obviously  "  acid  "  soap, 
the  mixture  turns  pink  or  bright  red  as  the  added  water  is 
increased.  The  opposite  type  of  experiment  may  be  made  by 
adding  an  excess  of  sodium  hydroxid  to  the  sodium  oleate. 
Under  such  circumstances  the  mixture  may  assume  a  pinkish 
tinge,  but  this  is  because  the  excess  of  sodium  hydroxid  is  hydrated 
and  separates  out  in  emulsified  form  in  the  chemically  "  neutral  " 
sodium  oleate.1  It  is  not  the  hydrated  soap  but  the  hydrated 
sodium  hydroxid  which  turns  pink.  When  instead  of  sodium 
hydroxid,  sodium  chlorid  is  used,  such  pinking  of  the  system  does 
not  follow.  Hydration  of  the  neutral  salt  occurs  and  the  mixture 
becomes  more  viscid,  just  as  when  sodium  hydroxid  is  added,  but 
since  sodium  chlorid  is  neutral  and  since  the  soap  is  not  soluble  in 
the  salt-water  no  change  in  the  color  of  the  indicator  becomes 
manifest. 

1  See  page  93  on  the  salting  out  of  soaps. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  81 


§2 

We  emphasize  these  points  because  in  technological  practice 
it  is  often  of  much  importance  to  know  whether  the  system 
worked  upon  is  "  acid,"  "  alkaline  "  or  "  neutral "  in  reaction. 
The  above  observations  may  serve  to  show  with  what  extreme 
care  any  deductions  derived  from  the  application  of  indicator 
methods  (or  other  methods  of  determining  hydrogen  or  hydroxyl 
ion  concentration)  must  be  applied  to  such  systems  if  they  are  of 
the  lyophilic  colloid  type.  The  indicators  may  help  us  for  those 
portions  of  the  system  which  are  of  the  composition  x-dissolved-in- 
water  but  they  do  not  necessarily  tell  us  anything  of  those  portions 
composed  of  water-dissolved-in-x. 

With  regard  to  the  specific  problem  of  soap  manufacture,  we 
may  say  that  the  proportions  of  fat  (or  fatty  acid),  alkali  and 
water  as  chosen  in  common  practice  are  such  as  yield  only  water- 
in-soap  types  of  systems  when  the  cold  process  is  followed.  The 
same  is  true  for  the  cooled  systems  when  the  soap  is  made  by  the 
hot  process  and  independently  of  whether  the  soap  has  been  salted 
out  (by  sodium  chlorid)  or  not.  While  the  soap  is  boiling  it 
represents  a  mixture  of  water-in-soap  and  soap-in-water.  If  indi- 
cator methods  are  used  on  such  a  system  and  at  higher  tempera- 
tures this  much  may  be  said  for  them.  Any  boiling  soap  which  is 
just  alkaline  to  phenolphthalein  (decidedly  pink)  will  be  less  alkaline 
(colorless)  when  cooled.  It  may,  on  cooling,  stitt  contain  free  fatty 
acid,  but  it  will  not  hold  uncombined  alkali. 

We  have  already  emphasized  the  important  applications  of 
these  principles  to  various  biochemical  reactions  and  to  problems 
in  biology  and  medicine.1  We  shall  return  to  the  problem  later.2 
Suffice  it  at  this  time  to  emphasize  the  fact  that  the  reactions  in  the 
solid  tissues  of  the  body  (including  for  the  most  part  those  in  the 
major  portions  of  the  blood  and  lymph)  are  reactions  in  a  medium 
analogous  to  a  concentrated  soap.  The  reactions,  on  the  other 
hand,  occurring  in  the  watery  secretions  from  the  body  (like  the 
urine  and  sweat)  occur  for  the  most  part,  in  a  system  analogous 
to  diluted  soap.  Indicator  methods  may  be  applied  and  with  a 
fair  degree  of  accuracy  only  to  the  latter  systems;  their  applica- 

1  See  MARTIN  H.  FISCHER:  (Edema  and  Nephritis,  2nd  Ed.,  324,  512,  629, 
New  York  (1915);  3rd  Ed.,  368,  642,  765,  New  York  (1921). 

2  See  page  229. 


82  SOAPS  AND  PROTEINS 

tion  to  the  former  type  of  system  must  be  carried  out  with  the 
greatest  caution,  if,  indeed,  they  may  be  used  at  all.  Yet  it  is 
the  common  practice  of  biochemists  and  biological  workers  to 
hold  that  protoplasm,  too,  is  something  analogous  to  a  dilute 
solution. 

The  observations  detailed  above  carry  with  them  an  inter- 
esting corollary.  The  color  changes  of  indicators  are  in  the  major- 
ity of  instances  assumed  to  be  dependent  upon  a  play  between  the 
concentration  of  the  electrically  charged  hydrogen  and  hydroxyl 
ions.  If  this  assumption  is  held  true  for  phenolphthalein  (or  for 
any  other  indicator  which  is  held  to  act  in  this  fashion),  and 
especially  if  any  one  maintains  that  such  indicator  methods  may 
be  applied  to  concentrated  lyophilic  colloid  systems,  then  the 
conclusion  is  inevitable  that  these  concentrated  systems  contain  no 
such  ions.  The  matter  is  of  significance  because  living  matter 
(normal  protoplasm)  does  not  behave,  as  is  so  widely  assumed,  as 
water  containing  a  little  colloid,  but  rather  as  a  colloid  contain- 
ing some  water.1  If  this  be  true — and  all  experimental  evidence 
supports  such  a  conclusion — then  the  material  which  we  call  living 
matter  is  probably  under  normal  circumstances  as  electrically  bland 
as  is  a  concentrated  soap  solution,  a  conclusion  not  to  be  overlooked 
in  a  day  when  the  explanation  of  almost  every  fundamental  life 
process  has  been  assumed  to  have  been  found  in  an  electrical 
notion  of  some  kind.  This  criticism  is  not  to  be  misunderstood. 
Differences  in  electrical  potential,  in  ionization,  etc.,  do  come 
about  in  living  matter,  but  they  are  more  probably  the  results  of 
and  the  expression  of  injury  to  the  involved  structures  than 
of  their  normal  life. 

1  MARTIN  H.  FISCHER:  (Edema  and  Nephritis,  3rd  Ed.,   New  York  (1921) 
where  references  to  the  first  publications  on  this  subject  may  be  found. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  83 


VIII 
ON   THE   PHYSICAL   STATE   OF   SOAP   MIXTURES 

The  experiments  previously  detailed  show  that  the  different 
soaps  differ  among  themselves  in  their  absolute  gelation  capacities. 
Speaking  generally,  linolates  hold  less  of  various  "  solvents " 
(like  water)  than  chemically  comparable  amounts  of  the  oleates, 
and  these  hold  less  than  equimolar  amounts  of  the  stearates. 
Within  the  acetic  series  itself  the  lower  members  are  less  hydra- 
table  than  the  upper.  The  question  therefore  arose  as  to  what 
would  happen  if  two  such  soaps  of  different  hydration  capacities 
competed  for  a  fixed  volume  of  water.  This  is,  in  essence,  the 
question  of  technological  importance  when  in  commercial  soap 
manufacture  a  mixed  soap  is  prepared  in  a  limited  volume  of 
water  from  the  mixture  of  fatty  acids  obtained  from  any  ordinary 
mixed  glycerid. 

A  first  experiment  under  this  head  was  made  by  adding  to 
a  hot  sodium  stearate  solution  increasing  amounts  of  hot  sodium 
oleate.  The  actual  mixtures  are  shown  in  Table  XXII. 

The  soaps  were  added  to  each  other  at  the  temperature  of  a 
boiling  water  bath  and,  after  careful  mixing,  were  allowed  to  cool 
to  18°  C.  The  results  of  this  experiment  are  shown  in  Fig.  51. 
As  indicated  in  the  first  bottle  on  the  left,  sodium  oleate  is,  even 
at  the  maximal  concentration  employed  in  the  series,  a  mobile 
liquid.  The  bottle  on  the  extreme  right  shows  that  sodium  stea- 
rate at  the  concentration  chosen  is  a  white  solid.  As  evidenced 
in  the  bottles  between  these  two  extremes,  the  presence  of  the 
sodium  oleate  interferes  with  the  solidification  of  the  whole  mix- 
ture. Even  when  these  mixtures  are  kept  standing  for  months 
they  do  not  go  solid. 

A  second  experiment  under  this  heading  was  made  by  adding 
sodium  oleate  to  sodium  palmitate.  The  mixtures,  prepared  in 
a  boiling  water  bath,  had  the  composition  shown  in  Table  XXIII. 

The  appearance  of  these  mixtures  on  cooling  to  18°  C.  is  shown 
in  Fig.  52.  While  the  sodium  palmitate  will  by  itself  yield  a  white 
solid,  admixture  with  sodium  oleate  prevents  this,  arid  does  so 


84 


SOAPS  AND  PROTEINS 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


85 


86 


SOAPS  AND  PROTEINS 


in  increasing  degree  with  its  concentration  in  the  mixture.  In 
the  mixtures  containing  the  larger  amounts  of  sodium  oleate, 
the  sodium  palmitate  floats  in  masses  of  silky  needles  within  a 
liquid  menstruum. 


In  a  third  experiment  the  effects  of  mixing  sodium  linolate 
with  sodium  stearate  were  studied.  The  composition  of  the 
mixtures  is  given  in  Table  XXIV.  Fig.  53  shows  that  when 
the  previously  clear  mixtures  prepared  in  a  boiling  water  bath 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


87 


are  cooled  to  18°  C.  the  linolate  with  its  lower  absolute  gelation 
capacity  again  dominates  the  mixture.  While  the  pure  stearate 
is  solid,  admixture  with  sodium  linolate  yields  increasingly  softer 
or  liquid  systems. 


A  final  experiment  was  made  by  mixing  two  soaps  of 
the  same  series,  namely,  sodium  capiylate  with  sodium  stearate 
as  indicated  in  Table  XXV.  The  results  of  this  experiment  are 
visible  in  Fig.  54.  The  physical  state  of  the  soap  mixtures  is 


88  SOAPS  AND  PROTEINS 

again    dominated  by  the  soap  of  the  lesser    absolute    gelation 
capacity. 

These  several  experiments  show,  therefore,  that  in  any  soap 
mixture  it  is  the  soap  with  the  lower  absolute  gelation  capacity 
which  gives  the  deciding  character  to  the  mixture.  In  trying 
to  account  for  this,  it  is  of  interest  to  point  out  that  the  simpler 
soaps,  or  those  lowest  in  any  series,  stand  closer  to  the  ordinary 
"  salts  "  of  the  physical  chemists  than  do  the  more  complex  or 
higher  soaps.  The  lower  soaps,  as  it  were,  "  salt-out  "  the  higher 
ones  as  do  the  ordinary  neutral  salts  when  added  to  the  soaps. 
This  matter  will  be  discussed  later.1 


TABLE   XXII 

SODIUM  OLEATE — SODIUM  STEARATE  MIXTURES 


(1)  35      cc.  m/2  sodium  oleate  +  70      cc.  HzO  (control) 


(2)  7. See.  '  +27.5cc.       '    +  70  cc. 

(3)  15  co.  '  '  +20      cc.       '    +70  cc. 

(4)  20  co.  '  '  '       +15      cc.       '    +70  cc. 

(5)  25  cc.  '  '  +10      cc.       '    +70  ce. 

(6)  30  cc.  '  +   5      cc.       '    +70  cc. 

(7)  35  cc.  '  '  '       +70      cc.  m/10  sodium  £ 

(8)  35  cc.  HiO  +  70  cc.  m/10  sodium  stearate  (control) 


m/10  sodium  stearate 


TABLE   XXIII 

SODIUM  OLEATE — SODIUM  PALMITATE  MIXTURES 

(1)   35  cc.  m/2  sodium  oleate  +  70  cc.  HiO  (control) 


(2)  5cc.  '  +30  cc. 

(3)  10  cc. +25  cc. 

(4)  15  cc. +20  cc. 

(5)  20  cc. +15  cc. 

(6)  25  cc. +10  cc. 

(7)  30  cc. +5  cc. 

(8)  35  cc.  "          "  "  +70  cc.  m/10  sodium  palmitate 

(9)  35  cc.  HjO  +  70  cc.  m/10  sodium  palmitate 


+  70  cc.  m/10  sodium  palmitate 

+70  cc.     " 

+70  cc.     " 

+  70  cc.     " 

+70  cc.     " 

+70  cc.     " 


TABLE   XXIV 

SODIUM  LINOLATE — SODIUM  STEARATE  MIXTURES 

(1)  35  cc.  m/2  sodium  linolate  +  70  cc.  HiO  (control) 


(2)  5cc. 

(3)  10  cc. 

(4)  15  cc. 

(5)  20  cc. 

(6)  25  cc. 

(7)  30  cc. 

(8)  35  cc. 


+30  cc.  "  +70  cc.  m/10  sodium  stearate 

+25  cc.  "  +70  cc.      " 

+  20  cc.  "  +70  cc.      " 

.  ].-,  ,.,.  ••  +70  cc.      " 

+  10cc.  "  +70  cc.      " 

+  5  cc.  "  +70  cc       " 

+70  cc.  m/10  sodium  stearate 


(9)  35  cc.  HjO  +  70  cc.  m/10  sodium  stearate 


1  See  page  93. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


TABLE   XXV 

SODIUM  CAPRYLATE — SODIUM  STEARATE  MIXTURES 

(1)  30      cc.  4  msodiumcaprylate  +  70  cc.  HzO  (control) 

+  29  cc.  +70  cc.   m/ 10  sodium  stearate 

+  27.5  cc.  +70  cc. 

+  25  cc.  +70  cc. 

+  20  cc.  +70  cc. 

+  15  cc.  +70  cc. 

+  10  cc.  +70  cc. 

+  5  cc.  +70  cc. 

+  70  cc.  m/10  sodium  stearate 


(2)     1      cc.  < 

I  m 

(3)     2.5  cc. 

m 

(4)     5      cc. 

m 

(5)   10      cc. 

m 

(6)    15      cc. 

m 

(7)  20      cc. 

m 

(8)   25      cc. 

m 

(9)   30      cc. 

m 

(10)  30      cc.  ] 

S20+70 

IX 


ON   REVERSIBILITY  IN   SOAPS 

§1 

We  noted  early  in  our  experiments  that  the  physical  con- 
stants of  the  alkaline  earth  and  heavy  metal  soaps,  as  ordinarily 
prepared  by  precipitation  of  a  sodium  or  potassium  soap  with 
the  salt  of  a  heavier  metal,  were  different  from  those  of  these 
same  soaps  when  prepared  directly  from  a  proper  fatty  acid  and 
a  metallic  hydroxid  or  oxid.  We  attributed  the  differences  to 
admixture  of  the  heavy  metal  soap  with  the  original  soap.  As 
a  matter  of  fact,  we  always  deal  in  soaps  thus  prepared  with  a 
mixture,  in  equilibrium,  of  the  two  soaps.  In  order  to  study  the 
matter  further  we  performed  the  following  experiments  on  the 
reversion  of  soaps  of  the  alkaline  earths  and  the  heavy  metals 
into  the  soaps  of  the  alkali  metals  under  the  influence  of  alkali 
hydroxids. 

The  results  in  the  case  of  a  series  of  oleates  may  be  thus  illus- 
trated.    Molar  equivalents  of  the  hydrated  oleates  pictured  in 
Fig.  2  and  described  in  Table  III  were  placed  in  separate  vials. ' 
The  actual  amounts  were  as  follows : 

Magnesium  oleate 5.1  grams 

Calcium  oleate 3.8  grams 

Lead  oleate 4.2  grains 

Mercury  oleate 4.2  grams 

Barium  oleate 3.6  grams 

These  soaps  were  covered  with  10  cc.  normal  KOH  (the  amount 
necessary  to  convert,  if  possible,  all  the  heavy  soap  into  potassium 
soap).  The  appearance  of  the  soaps  immediately  after  addition 


90 


SOAPS  AND  PROTEINS 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


91 


92  SOAPS  AND  PROTEINS 

of  the  alkali  is  shown  in  the  upper  row  of  Fig.  55.  Within  an 
hour  after  adding  the  potassium  hydroxid  all  the  soaps  began 
to  swell  and  to  become  covered  with  gelatinous  films.  This 
change  to  potassium  oleate  was  particularly  rapid  in  the  mag- 
nesium and  lead  soaps.  But  it  occurred  in  all,  so  that  after  an 
hour  enough  potassium  soap  was  formed  to  make  the  liquids 
covering  the  metallic  soaps  show  permanent  foams. 

These  changes  occur  in  the  cold  and  even  when  the  reaction 
mixtures  are  not  stirred.  Heating  and  stirring,  however,  hasten 
the  process.  In  either  event  a  high  degree  of  reversion  is  obtained 
as  indicated  by  the  lower  row  of  Fig.  55,  which  shows  the  appear- 
ance of  the  soap  mixtures  after  standing  at  room  temperature 
for  forty-eight  hours.  So  much  potassium  oleate  had  formed 
that  all  the  systems  were  highly  gelatinous. 

A  similar  reversion  from  the  stearates  of  the  alkaline  earths 
and  the  heavy  metals  into  sodium  stearate  is  shown  in  Fig.  56. 
The  upper  row  shows  the  vials  with  their  molar  equivalents  of 
the  different  stearates  prepared  as  described  in  Table  IV  (and 
Fig.  3),  just  after  10  cc.  normal  sodium  hydroxid  had  been  added 
to  them.  The  actual  amounts  of  soap  in  the  vials  were  as  follows : 

Magnesium  stearate 9 . 60  grams 

Calcium  stearate 7 . 05  grams 

Mercury  stearate 8 . 65  grams 

Lead  stearate 7 . 30  grams 

Barium  stearate 5 . 87  grams 

After  addition  of  the  sodium  hydroxid  the  mixtures  were  kept 
warm  for  one  hour  at  75°  C.  The  appearance  of  the  same  soap 
mixtures  forty-eight  hours  later  is  shown  in  the  lower  row  of 
Fig.  56.  The  reversion  to  sodium  stearate  is  so  great  that  all 
the  mixtures  are  now  solid  gels. 


§2 

These  experiments  on  reversion  in  soaps  are  of  chief  interest 
to  us  because  the  soaps  in  their  colloid-chemical  behavior  are  like 
the  proteins  of  .the.  living  cell.  The  heavy  metal  soaps  are  like 
the  heavy  metal  proteinates  which  are  produced  when  the  living 
cell  is  poisoned  with  lead,  mercury,  etc.;  and  just  as  the  heavy 
metal  soaps  may  be  converted  into  those  of  the  lighter  metals, 
cells  poisoned  with  heavy  metals  may  be  aided  in  their  restoration 


THE  COLLOID-CHEMISTRY  OF  SOAPS  93 

to  the  more  normal  state  by  the  administration  of  properly 
chosen  salts  of  the  lighter  metals.1 

There  exist,  however,  processes  in  pure  soap  manufacture 
which  have  long  made  empiric  use  of  the  facts  detailed  above. 
Instead  of  hydrolyzing  fats  with  sodium  or  potassium  hydroxid, 
they  are  often  hydrolyzed  with  calcium  hydroxid.  Under  such 
circumstances  calcium  soaps  are  produced  which,  as  formed,  have 
little  or  no  "  washing  "  properties.  The  calcium  soaps  are  then 
converted  into  sodium  or  potassium  soaps  by  treatment  with 
the  carbonates  of  these  metals. 


X 

ON  THE    "SALTING-OUT"  OF   SOAPS2 

The  previous  pages  3  have  shown  that  the  absorption  of  water 
by  various  pure  soaps  (and  hence  their  physical  state)  depends 
upon  (a)  the  kind  of  base  combined  with  a  given  fatty  acid,  or, 
with  a  given  base  (6)  upon  the  nature  of  the  fatty  acid.  It  is 
the  purpose  of  this  section  to  describe  the  influence  which  the 
addition  of  different  electrolytes  has  upon  their  physical  state. 
We  shall  first  describe  the  action  of  different  salts  upon  a  single 
soap,  namely,  potassium  oleate;  later  the  effects  of  one  salt 
upon  different  soaps.  The  practical  and  theoretical  deductions 
drawn  from  these  materials  will  then  be  correlated  with  the  vari- 
ous empiric  practices  of  the  soap  manufacturer  and  allied  scien- 
tific studies  in  this  field. 

1.  On  the "  Salting-Out"  of  Potassium  Oleate 

The  potassium  oleate  used  in  these  experiments  was  prepared 
by  adding  to  the  molar  weight  of  oleic  acid  expressed  in  grams 
(282.27)  1000  cc.  of  a  normal  KOH  solution.  The  oleic  acid 
and  the  potassium  hydroxid  solution  were  heated  separately  in 
a  water  bath  and,  at  the  temperature  of  the  boiling  water,  the 

1  See  page  240. 

2  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Science,  48,  143  (1918); 
ibid.,  49,  615  (1919);    Chem.  Engineer,  27,  225  and  253  (1919).    See  also 
page  205. 

'See  pages  10  and  15;  also  MARTIN  H.  FISCHER  and  MARIAN  O. 
HOOKER:  Chem.  Engineer,  27,  155  (1919);  ibid.,  27,  184  (1919). 


94  SOAPS  AND  PROTEINS 

oleic  acid  was  poured  into  the  potassium  hydroxid.  The  mix- 
ture was  stirred  and  heated,  with  careful  avoidance  of  evapo- 
ration, until  a  clear,  viscid  liquid  was  obtained.  Whenever  our 
stock  or  standard  potassium  oleate  solution  is  mentioned  in  the 
following  experiments  one  prepared  in  this  fashion  is  referred  to. 
At  room  temperature  this  stock  is  strongly  alkaline  to  litmus 
paper  but  phenolphthalein  when  added  to  it  remains  colorless.1 

1.  We  tested  out,  first,  the  effects  of  adding  different  amounts 
of  water  to  the  standard  potassium  oleate.     The  stock  soap  when 
prepared  as  described  has  the  viscosity  of  a  syrup  at  ordinary 
temperatures   (18°  C.).     The  addition  to  this  of  progressively 
greater  amounts  of  water  merely  serves  to  decrease  its  viscosity. 

2.  We  next  tried  the  effects  of  adding  progressively  greater 
amounts  of  various  alkalies  (KOH,  NaOH  and  NIrUOH)  to  the 
standard    soap.     While  from  a  chemical    standpoint  it  matters 
little  how  a  mixture  is  made,  it  makes  much  difference  from  a 
physical  point  of  view  as  will  be  discussed  later.     When  not 
otherwise  specified  the  mixtures  throughout  these   series  were 
made  in  the  sequence  in  which  they  appear  in  the  tables.     In  Table 
XXVI,  for  instance,  the  water  was  first  added  to  the  soap  and 
mixed;    then  the  KOH  solution  was  added  and  the  whole  again 
mixed.     When   not   otherwise   specified,    all   combinations   were 
made  at  room  temperature  which  in  the  room  employed  and  at 
the  time  at  which  we  worked   (the  winter  of  1917  and   1918) 
remained   continuously  close  to   18°  C.     The  descriptions  and 
photographs  refer  to  the  appearance  of  the  mixtures  twenty-four 
hours  later. 

Table  XXVI  and  Fig.  57  show  the  effects  of  adding  potassium 
hydroxid.  It  is  obvious  that  the  control  soap  with  water  mix- 
ture is  a  mobile  liquid.  The  first  additions  of  potassium  hydroxid 
to  this  mixture  serve  to  increase  its  viscosity  as  evidenced  in  the 
tubes  marked  1,  2,  3  and  4.  But  beyond  this  point  further 
addition  of  the  potassium  hydroxid  begins  to  bring  about  a 
dehydration  of  the  soap  which  increases  progressively  until,  in 
the  tube  marked  10,  the  soap  is  found  floating  as  a  thin  layer 
at  the  top  of  the  clear  dispersion  medium. 

The  effects  of  sodium  hydroxid  upon  the  standard  potassium 
oleate  are  similar  to  those  of  potassium  hydroxid  as  apparent  in 

1  See  page  77  for  a  discussion  of  the  meaning  of  indicator  methods  when 
applied  to  these  soap  systems. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  95 

Table  XXVII  and  Fig.  58.  There  is  at  first  a  progressive  increase 
in  viscosity  until  a  beautiful  gel  is  formed.  Further  addition 
of  the  alkali  then  brings  about  a 
separation  of  the  soap  from  the 
water  as  already  described  for 
potassium  hydroxid. 

Table  XXVIII  and  Fig.  59 
show  that  none  of  these  things 
happen  when  equinormal  ammo- 
nium hydroxid  is  added  to  the 
potassium  oleate.  In  fact,  even 
if  the  concentrations  of  the 
ammonium  hydroxid  are  carried 
beyond  those  in  the  table  no 
gelation  and  no  separation  of 
the  soap  occurs.  The  reasons 
for  this  are  discussed  later. 

The  fact  of  interest  in  these 
parallel  series  of  experiments  is 
that  the  sodium  hydroxid  leads 
to  increase  in  viscosity  and  the 
setting  of  the  soap  into  a  solid 
jelly  at  a  somewhat  lower  con- 
centration than  is  the  case  for 
potassium  hydroxid;  and  this 
same  shifting  of  effect  toward 
the  left  is  true  of  the  separation 
of  the  soap  from  the  aqueous 
dispersion  medium  in  the  higher 
concentrations  of  the  alkali. 
To  the  meaning  of  these  things 
we  shall  return  later. 

3.  We  next  compared  the 
effects  of  a  group  of  salts  having 
a  common  base  and  different  acid 
radicals.  To  simplify  matters 
a  series  of  potassium  salts  was 
chosen. 

The  effect  of  the  halogens    is  shown  in  Tables  XXIX,  XXX, 
XXXI  and  XXXII.     Photographs  of  the  chlorid  and  bromid 


96 


SOAPS  AND  PROTEINS 


series  are  shown  in  Figs.  60  and  61.  It  is  obvious  from  the  tables 
and  the  figures  that  these  neutral  salts  behave  in  the  same  general 
fashion  as  the  previously  described  hydroxids.  With  progressive 
increase  in  concentration  there  is  observed  in  all  the  series  a  pro- 
gressive increase  in  viscosity  of  the  soap  until  it  sets  into  a  stiff 
jelly.  With  further  addition  of  the  salt  the  viscosity  falls,  a  slight 
turbidness  develops  and,  later  still,  separation  of  the  soap  from 
the  dispersion  medium  sets  in.  This  separation  finally  becomes 
so  great  that  the  soap  floats  as  a  practically  dry  white  mass  upon 
the  underlying  clear  dispersion  medium.  Some  difference  seems 
to  exist  in  the  power  with  which  the  four  halogens  lead  to  the 
setting  of  the  soap  and  its  subsequent  dehydration  and  separation. 
The  difference  may,  however,  be  one  of  experimental  error  only. 


FIGURE  58. 

It  is  exceedingly  difficult,  as  everyone  knows  who  has  worked 
quantitatively  in  these  fields,  to  be  sure  of  getting  absolutely 
equal  rates  and  degrees  of  mixing  and  thus  absolutely  equal 
effects  when  producing  these  various  systems. 

Of  other  monobasic  potassium  salts  the  effects  of  the  nitrate, 
sulphocyanate  and  acetate  have  been  studied.  Potassium 
nitrate  acts  very  much  like  potassium  chlorid  as  shown  in  Fig.  62 
and  Tables  XXXIII  and  XXXIV.  With  increasing  concentra- 
tion of  the  added  salt  the  soap  first  gels  and  then  softens,  though 
the  solubility  limits  of  potassium  nitrate,  as  seen  in  mixtures  9 
and  10  of  Table  XXXIV  are  such  as  to  lead  to  the  formation  of 
nitrate  crystals  in  the  tubes  and  not  to  an  actual  dehydration 
and  separation  of  the  soap  from  the  dispersion  medium. 

The  range  from  a  liquid  to  a  gel,  through  a  secondary 
zone  of  liquefaction  succeeded  by  dehydration  of  the  soap  and 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


97 


separation  of  the  clear  dispersion  medium,  is  seen  particularly 
clearly  in  the  case  of  potassium  sulphocyanate.     The  concentra- 


tions necessary  for  these  successive  changes  may  be  deduced 
from  Tables  XXXV,  XXXVI  and  XXXVII.  The  actual  appear- 
ance of  the  tubes  described  in  Table  XXXVII  is  shown  in  Fig.  63. 


98 


SOAPS  AND  PROTEINS 


Table  XXXVIII  and  Fig.  64  show  the  effects  of  potassium 
acetate.  As  compared  with  the  action  of  the  other  potassium 
salts  thus  far  described,  it  will  be  seen  that  at  equimolar  con- 
centrations this  acts  more  powerfully.  The  soap  passes  through 


all  the  various  changes  to  complete  dehydration  even  within  the 
short  range  of  concentrations  detailed  in  the  single  table. 

The  effects  of  several  potassium  salts  of  polybasic  acids  are 
shown  in  Tables  XXXIX,  XL,  XLI  and  XLII  and  Figs.  65,  66, 
67  and  68.  Dipotassium  sulphate  and  dipotassium  tartrate  pro- 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


IOC' 


SOAPS  AND  PROTEINS 


THE  COLLOID-CHEMISTRY  OF  SOAPS: 


VIM 


duce  results  practically  identical  with  those  of  the  potassium 
halogens  when  the  effects  of  adding  half  molar  concentrations 
of  the  former  salts  are  compared  with  those  of  molar  concentra- 
tions of  the  halogens. 

Because  of  the  limited  solubility  of  potassium  sulphate  and 
of  dipotassium  tartrate,  Tables  XXXIX  and  XL  and  Figs.  65 
and  66  only  serve  to  show  that  with  increase  in  the  concentration 
of  the  added  salts  there  is  progressive  increase  in  the  viscosity 
of  the  soap  until  gelation  or,  beyond  this,  a  secondary  lique- 
faction occurs  in  the  highest  concentrations  here  employed. 


FIGURE  66. 

However,  by  working  at  higher  temperatures  the  concentration 
of  both  the  sulphate  and  the  tartrate  may  be  increased  to  a  point 
where  the  soap  is  "  salted-out." 

Tables  XLI  and  XLII  with  Figs.  67  and  68  show  the  effects 
of  adding  the  potassium  salts  of  two  tribasic  acids.  Dipotassium 
phosphate  (Fig.  67)  and  tripotassium  citrate  (Fig.  68)  in  increasing 
concentrations  at  first  lead  to  gelation,  then  liquefaction  and 
finally  complete  dehydration  of  potassium  oleate.  When  compared 
with  the  action  of  monovalent  salts,  the  tables  and  figures  show 
that  the  initial  gelations  are  obtained  at  about  the  same  molar 
concentrations  of  the  potassium  constituent  of  the  systems, 
though  subsequent  liquefaction  and  dehydration  occur  somewhat 


..102 


SOAPS  AND  PROTEINS 


earlier  in  the  case  of  the  polyvalent  acid  radicals  than  in  that 
of  the  simpler  ones. 

4.  The  next  problem  was  to  determine  the  effects  of  adding 
alkali  and   salt  together  to  potassium   oleate.     The  effects  of 


•»*»»*• * 

- 


FIGURE  67. 

different  concentrations  of  potassium  chlorid  added  to  standard 
potassium  oleate,  containing  two  different  concentrations  of  potas- 
sium hydroxid,  are  shown  in  Tables  XLIII  and  XLIV. 

So  far  as  concentration  of  the  potassium  hydroxid  is  con- 
cerned, Table  XLIII  must  be  compared  with  the  second  tube 


FIGURE  68. 

of  Fig.  57  (Table  XXVI);  so  far  as  the  concentration  of  potassium 
chlorid  is  concerned,  with  the  first  five  tubes  of  Fig.  60  (Table 
XXX).  When  this  is  done  it  is  observed  that  the  effects  of  the 
alkali  and  of  the  added  potassium  chlorid  are  additive.  In  other 
words,  gelation  and  secondary  liquefaction  are  apparent  earlier 
in  the  series  in  Table  XLIII  than  in  the  corresponding  tubes  of 
Figs.  57  and  60. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  103 

The  alkali  concentration  of  Table  XLIV  corresponds  with  that 
of  tube  4  in  Fig.  57  (Table  XXVI).  The  non-dehydrating  effects 
of  the  concentrations  of  potassium  chlorid  employed  are  clearly 
apparent  by  referring  to  Fig.  60  and  Table  XXX.  While  the 
concentration  of  alkali  alone  leads  only  to  gelation  of  the  potas- 
sium oleate,  it  will  be  seen  in  Table  XLIV  that  the  effect  of  the 
potassium  chlorid  adds  itself  to  this,  wherefore  the  first  tube  in 
the  series  shows,  a  beginning  dehydration  which,  with  increase 
in  the  concentration  of  the  added  salt,  becomes  progressively 
greater  until  marked  dehydration  and  separation  from  the  clear 
dispersion  medium  is  evident  in  the  last  tube. 

Table  XLV  shows  that  such  an  additive  effect  is  apparent 
also  when  in  the  presence  of  a  fixed  concentration  of  potassium 
chlorid  different  amounts  of  standard  potassium  hydroxid  solu- 
tion are  added  to  the  standard  potassium  oleate.  While  neither 
of  the  substances  when  used  alone  and  in  the  concentrations 
prevailing  in  the  first  tube  lead  to  gelation,  the  two  together  do 
so.  When  comparison  is  made  with  the  proper  tubes  of  Figs. 
57  and  60,  it  is  also  apparent  that  the  secondary  liquefaction 
and  the  dehydration  begin  earlier  when  alkali  and  salt  are  used 
together  than  when  either  is  used  alone. 

To  complete  this  series,  we  add  Tables  XL VI  and  XL VII. 
In  Table  XL VI  the  concentration  of  potassium  hydroxid  is  fixed 
and  that  of  sodium  chlorid  varies,  while  in  Table  XL VI I  the 
concentration  of  sodium  chlorid  is  fixed  and  that  of  potassium 
hydroxid  varies.  These  tables  should  be  compared  with  Tables 
XXVI  and  XLIX,  or  Figs.  57  and  70.  Such  comparison  shows 
that  gelation  with  subsequent  liquefaction  and  dehydration  are 
obtained  earlier  when  the  alkali  and  chlorid  are  present  together 
than  when  either  is  used  alone  in  the  concentration  chosen.  When 
the  effects  of  sodium  chlorid  are  compared  with  those  of  potassium 
chlorid,  it  is  again  apparent  that  the  sodium  salt  acts  more  power- 
fully; in  other  words,  the  systems  are  shifted  toward  the  regions 
of  earlier  gelation,  earlier  dehydration  and  earlier  separation. 

5.  We  next  tried  the  effects  of  adding  in  equimolar  concen- 
trations various  salts  possessed  of  a  common  acid  radical  but 
different  bases.  We  chose  chlorids. 

In  Table  XL VIII  and  Fig.  69  (introduced  as  checks  on  Table 
XXX  and  Fig.  60  and  on  the  experiments  about  to  be  described) 
are  shown  the  effects  of  adding  successively  higher  concentra- 


104 


SOAPS  AND  PROTEINS 


tions  of  potassium  chlorid.     The  control  tube  shows  the  familiar 
liquid  soap.     With  progressive  increase  in  the  concentration  of 


the  salt,  the  viscosity  of  the  soap  mounts  steadily  until  in  the 
tube  marked  10  such  a  solid  gel  is  obtained  that  the  tube  may 
be  turned  upside  down  without  spilling  the  contents. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


105 


Sodium  chlorid  produces  the  same  general  effects  as  potassium 
chlorid,  as  shown  in  Table  XLIX  and  Fig.  70.  When  the  effects 
of  the  two  salts  are  compared  it  is  seen  that  •  at  the  same  molar 
concentration  the  sodium  salt  acts  more  powerfully  than  the  potas- 
sium salt.  Initial  increase  in  viscosity,  gelation  and  frank  sepa- 
ration of  dispersion  medium  from  the  soap  occur  earlier  through- 
out in  the  tubes  of  Fig.  70  than  in  those  of  Fig.  69. 

When  ammonium  chlorid  is  employed  in  the  same  concen- 
tration as  that  described  above  for  potassium  or  sodium  chlorid, 
an  initial  increase  in  viscosity  in  the  lower  concentrations  of  the 
ammonium  salt  is  not  to  be  observed.  The  first  effect  to  be  noted 
is  a  slight  clouding  of  the  soap  mixture  as  shown  in  Fig.  71  and 


FIGURE  71. 


Table  L.  As  more  of  the  ammonium  chlorid  is  added  a  white 
collar  appears  which  grows  progressively  in  thickness  until  the 
whole  contents  of  the  tube  appear  white.  Microsco{>ic  ex- 
amination shows  this  collar  to  be  an  emulsion  (of  freed 'fatty 
acid  in  the  remaining  hydrated  soap).1 

The  effects  of  magnesium  and  of  calcium  chlorid^  upon  potas- 
sium oleate  are  shown  in  Tables  LI  and  LII  and  Figs.  72  and  73. 
There  is  no  increase  in  viscosity  to  be  noted  in  either  series  but 
only  a  progressive  fall.  This  is  due  to  the  formation  of  the  so- 
called  "  insoluble  "  calcium  and  magnesium  soaps.  It  would 
be  better  to  say  that  the  change  is  due  to  the  formation  of  less 
hydratable  soaps  for,  as  previous  study  has  shown,2  the  magnesium 
and  calcium  soaps  absorb  much  less  water  than  the  corresponding 
notassium  soaps.  Since  magnesium  soap  holds  more  water  than 


1  See  pages  109,  136  and  175. 


2  See  page  10. 


106 


SOAPS  AND  PROTEINS 


calcium  soap  the  former  settles  out  with  greater  difficulty  than 
the  latter,  as  may  be  seen  by  comparing  Figs.  72  and  73.  In 
the  higher  concentrations  of  the  calcium  salt,  the  calcium  oleate 
comes  down  in  very  finely  divided  (colloid)  form  and  so  remains 


•ft* 


mil 


FIGURE  72. 

suspended  in  the  liquid  as  shown  in  the  tubes  marked  5  and  10 
of  Fig.  73. 

The  formation  of  the  metallic  soaps  with  their  extremely  low 
hydration  capacities  again  dominates  the  picture  when  cupric 
or  ferric  chlorid  is  added  to  potassium  oleate.  As  shown  in 


FIGURE  73. 

Tables  LIII  and  LIV  the  soaps  as  formed  tend  from  the  first  to 
collect  in  hard,  dry  lumps  within  the  freed  dispersion  medium. 
Matters  are  further  complicated  in  these  experiments  by  a  partial 
separation  of  fatty  acid  due  to  the  fact  that  the  added  salts  yield 
an  overplus  of  acid  on  solution  and  hydrolysis  in  water. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  107 

2.  Critical  and  Historical  Remarks 

a.  Introduction.  Considered  in  the  broad,  these  experiments 
descriptive  of  the  effects  of  different  alkalies  and  of  different 
neutral  salts  upon  soap  are  as  old  as  soap  manufacture  or  chemical 
industry  itself.  The  precipitation  of  "  insoluble  "  metallic  soaps 
by  the  addition  of  salts  of  the  heavy  metals  to  sodium  or  potas- 
sium soaps  is  a  familiar  procedure  in  the  manufacture  of  various 
paint  products;  the  addition  of  ammonium  hydroxid  to  wash 
waters  has  long  been  known  to  have  a  value  in  laundering  proc- 
esses not  shown  by  more  fixed  "  lyes  ";  and  the  "  salting-out  " 
of  soaps  through  the  addition  of  an  excess  of  the  alkali  used  in 
making  the  soap  or  by  the  addition  of  ordinary  sodium  chlorid 
is  a  century  or  more  old.  The  soap  chemists  are  also  familiar 
with  the  fact  that  in  the  salting-out  process  they  often  encounter 
a  "  gumming  "  of  their  soap  mixtures  or  find  that  these  "  go 
stringy."  Nevertheless,  experimental  details  covering  all  these 
general  subjects  in  more  than  partial  fashion  seem  still  to  be 
meagre,  and  the  nature  of  the  simplest  findings  seems  not  yet 
to  have  emerged  from  the  realm  of  harsh  debate. 

If  the  facts  and  theoretical  considerations  covering  the  hydra- 
tion  and  solvation  properties  of  the  pure  soaps  themselves  as 
previously  outlined  in  these  pages  l  are  kept  in  mind,  it  becomes 
possible,  we  think,  not  only  to  draw  together  under  a  common 
heading  many  of  the  empiric  facts  of  chemical  industry  but  to 
find  an  explanation  for  them  in  decidedly  simpler  terms  than 
seem  now  to  be  in  use.  Before  detailing  the  views  of  other 
workers  in  these  fields  we  wish  for  the  sake  of  clarity  to  divide 
the  experiments  of  this  section  into  three  groups.  While  the 
phenomena  discussed  in  any  one  of  these  commonly  appear  also 
in  a  second,  or  even  in  a  third,  such  division  will  help  to  make 
clear  what  it  is  that  dominates  behavior  in  each  of  the  groups. 

The  previous  pages  have  shown  that  it  is  important  to  dis- 
tinguish between  the  solubility  of  any  soap  in  water  and  the  solu- 
bility of  the  water  in  that  soap.  Of  immediate  interest  for  our 
purposes  is  the  fact  that  of  the  soaps  of  a  given  fatty  acid  but 
with  different  bases,  ammonium  soap  is  most  soluble  in  water, 
potassium  next  and  then  sodium.  The  soaps  of  the  alkaline 
earths  are  hardly  soluble  in  water  and  those  of  the  heavy  metals 

1  See  page  69. 


108  SOAPS  AND  PROTEINS 

are  generally  regarded  as  completely  insoluble.  Looked  at  the 
other  way  about,  the  first  named  are  the  best  solvents  for  water, 
while  the  alkaline  earth  soaps  take  a  middle  ground,  and  those 
of  the  heavy  metals  stand  last.  With  these  general  truths  in 
mind,  it  is  obvious  that  we  may  classify  the  effects  of  adding 
an  alkali  hydroxid  or  of  adding  any  salt  to  potassium  oleate  as 
follows : 

(1)  a  soap  is  formed  more  soluble  in  water  and  a  better 

solvent  for  water; 

(2)  a  soap  is  formed  less  soluble  in  water  and  a  poorer 

solvent  for  water; 

(3)  no  change    occurs  in    the  solubility  characteristics  of 

the  soap. 

The  last  covers,  perhaps,  the  item  of  greatest  practical  impor- 
tance, namely,  that  of  the  ordinary  salting-out  of  soaps,  and  that 
about  which  most  debate  has  centered;  but  since  in  practice  it 
is  rarely  seen  in  the  pure  form  outlined  in  our  experiments,  but 
is  more  or  less  blurred  through  the  simultaneous  action  of  pos- 
sibilities (1)  or  (2),  it  is  best  taken  up  last. 

(I)  A  soap  is  formed  more  soluble  in  water  and  a  better  solvent 
for  water.  This  happens  when  ammonium  hydroxid  is  added 
in  any  amount  whatsoever  to  a  potassium  (or  sodium)  soap. 
In  this  case  the  viscosity  of  the  soap  mixture  regularly  falls. 
This  behavior  of  ammonium  hydroxid  is  strikingly  different  from 
that  of  either  potassium  or  sodium  hydroxid,  either  of  which  first 
brings  about  a  gelation  of  the  soap  solution  followed  by  a  second- 
ary liquefaction  and  then  a  separation  of  the  dehydrated  soap 
from  the  dispersion  medium  (a  solution  of  the  alkali  hydroxid 
in  water).  The  effect  of  such  fixed  hydroxids  is  regularly  attrib- 
uted to  "  increases  in  alkalinity/'  "  increases  in  hydroxyl  ions  " 
and  the  vaguer  concepts  of  "  adsorption  "  and  "  permeability." 
It  is  obvious  that  all  such  explanations  are  inadequate,  for  with 
enough  ammonium  hydroxid  at  hand  any  degree  of  "  alkalinity  " 
or  any  number  of  "  hydroxyl  ions  "  ought  also  to  become  avail- 
able to  bring  about  the  effects  observed  with  the  fixed  alkalies, 
yet,  when  ammonium  hydroxid  is  used,  these  effects  never  do 
come  about.  The  reason  is  that  through  interaction  of  the  potas- 
sium (or  other)  soap  with  the  ammonium  hydroxid,  ammonium 
soap  is  formed,  and  this  is  more  soluble  in  water  than  the  original 
potassium  (sodium  or  other)  soap.  The  system  as  a  whole 


THE  COLLOID-CHEMISTRY  OF  SOAPS  109 

becomes  "  less  colloid/'  approximates  more  nearly  a  "  true  " 
solution,  and  hence  its  viscosity  can  only  fall. 

The  same  general  effect  of  the  ammonium  radical  is  still  appar- 
ent when  instead  of  ammonium  hydroxid  some  salt  like  ammonium 
chlorid  is  added  to  potassium  oleate  (see  Fig.  71  and  Table  L). 
Here  again  no  initial  increase  in  viscosity  is  to  be  observed.  Since, 
however,  ammonium  chlorid  is  the  salt  of  a  weak  base  with  a 
stronger  acid  the  secondary  effect  of  an  overplus  of  acid  formed 
through  hydrolysis  also  appears.  By  means  of  this  acid,  fatty 
acid  is  liberated  from  the  soap  and  then  remains  emulsified  in 
the  soap.  A  third  effect  is  exerted  in  this  illustration  by  the 
unchanged  ammonium  chlorid  and  the  newly  formed  potassium 
chlorid  which  exert  a  dehydrating  effect  (see  below)  upon  both 
of  the  soaps. 

These  ideas  may  be  further  verified  by  using  ammonium 
acetate.  There  is  still  no  perceptible  initial  increase  in  viscosity, 
and  since  the  salt  used  is  more  nearly  neutral,  fatty  acid  is  not 
set  free.  In  the  higher  concentrations  of  this  salt  the  soap  merely 
separates  out  in  the  usual  fashion. 

(2)  A  soap  is  formed  less  soluble  in,  and  a  poorer  solvent  for,  the 
dispersion  medium.     This  is  observed  when  magnesium,  calcium, 
iron  or  copper  salts  are  added  to  a  solution  of  potassium  (or 
sodium)   oleate.     Under  these   circumstances,   too,   the   systems 
as  a  whole  again  become  more  liquid,  though  it  is  not  in  this 
instance  because  the  soaps  formed  are  more  soluble  in  the  solvent 
or  more  hydratable  but  because  they  are  less  soluble  and  less 
hydratable  and  so  fall  out,  allowing  the  viscosity  of  the  pure 
solvent  (essentially  salt  water)  to  come  to  the  front.     In  con- 
trast to  the  systems  described  under  (1),  these  regularly  become 
milky  or  white  while  the  former  become  more  transparent  (unless 
some  secondary  change  like  the  liberation  of  fatty  acid  in  emulsi- 
fied form  supervenes). 

(3)  The  change  in  kind  of  soap  is  negligible  or  there  is  none  at 
all.     This  happens,  for  example,   when  potassium  hydroxid  or 
a  neutral  potassium  salt  is  added  to  a  potassium  soap.     Under 
these  circumstances,  with  increasing  concentration  of  the  added 
substances,  all  the  changes  described  in  the  above  experiments 
are  seen  to  occur.     There  is,  first,  an  increase  in  viscosity  which, 
if  the  amount  of  the  solvent  is  not  too  great,  results  in  gelation, 
followed  by  a  secondary  liquefaction  resulting  ultimately  in  com- 


110  SOAPS  AND  PROTEINS 

plete  separation  of  the  anhydrous  soap  from  the  dispersion  medium. 
Since  the  nature  of  the  changes  seen  under  these  circumstances 
covers  the  question  of  the  theory  of  the  "  salting-out  "  process 
in  soap  manufacture  (as  well  as  that  of  the  salting-out  process 
in  many  other  lines  of  chemical  industry),  and  since  many  attempts 
have  been  made  to  explain  these  changes,  it  is  well  to  interrupt 
our  general  argument  here  to  review  such  theories,  as  far  as  they 
are  known  to  us,  before  proceeding  further  with  suggestions  of 
our  own. 

b.  Historical  Remarks  on  the  "  Salting-out  "  of  Soaps.  F.  HOF- 
MEISTER  l  recorded  in  1888  what  seem  to  be  the  first  quantitative 
studies  in  this  field  when,  in  studying  the  "  water-attracting  " 
powers  of  various  salts,  he  determined  the  minimal  concentrations 
in  which  they  would  bring  about  the  separation  of  a  soap  from 
its  aqueous  dispersion  medium.  Finding  that  the  ordinary  mixed 
soaps  gave  inconstant  results,  he  set  out  to  discover  the  lowest 
concentrations  of  various  sodium  salts  necessary  to  bring  about 
a  beginning  turbidity  in  solutions  of  sodium  oleate.  In  determin- 
ing this  point  he  noted  that  his  soap  solutions  frequently  jellied. 
F.  BOTAZZI  and  C.  VICTOROW  2  detailed,  some  twenty  years  later, 
the  effects  on  viscosity  of  adding  sodium  hydroxid  to  a  Marseilles 
soap  solution.  Their  soap  (in  essence  sodium  oleate)  had  been 
dialyzed  and  contained  in  consequence  free  fatty  acid  and  what 
is  commonly  designated,  since  the  work  of  F.  KRAFFT  and  H. 
WiGLOw,3  "  acid  soap."  4  Addition  of  sodium  hydroxid  to  such 
dialyzed  soap  was  found  to  be  followed  by  an  increase  in  viscosity 
which  at  higher  concentrations  of  the  alkali  gave  way  to  a  decrease. 

1  FRANZ  HOFMEISTER:  Arch.  f.  exp.  Path.  u.  Pharm.,  25,  6  (1888). 

*F.  BOTAZZI  and  C  VICTOROW:  Accad.  Lincei,  19  (1910),  accessible  only 
as  review  in  Kolloid-Zeitschr.,  8,  220  (1911). 

»  F.  KRAFFT  and  H.  WIGLOW:  Her.  d.  deut.  chem.  Gesell.,  28,  2566  (1895). 

4  If  it  is  true,  as  generally  supposed,  that  the  fatty  acids  are  monobasic  it 
becomes  a  difficult  mental  maneuver  to  figure  out  how  a  partial  saturation 
of  the  replaceable  hydrogen  is  going  to  yield  an  "acid"  soap.  While  the 
concept  is  widely  accepted,  no  one  has  ever  isolated  such  an  acid  soap  and 
the  only  reason  for  believing  in  it  seems  to  depend  upon  the  fact  that  a  clear 
solution  or  jelly  may  be  obtained  when  a  fatty  acid  is  only  partially  neutralized 
with  alkali  in  the  presence  of  small  amounts  of  water.  But  these  are  the  ideal 
conditions  for  the  production  of  emulsions,  the  emulsions  in  this  case  consisting 
of  fatty  acid  in  hydrated  soap.  When  the  indices  of  refraction  of  fatty  acid 
and  of  hydrated  soap  lie  close  together  the  mixture  looks  homogeneous.  See 
MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Science,  43,  468  (1916); 
Fats  and  Fatty  Degeneration,  29  and  100,  New  York  (1917). 


THE  COLLOID-CHEMISTRY  OF  SOAPS  111 

J.  W.  McBAiN  and  MILLICENT  TAYLOR  1  observed  the  same  facts 
for  sodium  palmitate  at  90°  C.  Their  "  acid  "  sodium  palmitate 
was  first  rendered  "  more  colloidal  "  by  the  addition  of  sodium 
hydroxid  and  was  then  salted  out  entirely  in  concentrations  of 
the  hydroxid  above  1.5  normal. 

F.  GOLDSCHMIDT  and  L.  WEISSMANN  2  also  studied  the  changes 
in  viscosity  of  potassium  soap  solutions  when  various  electrolytes 
were  added  to  them.  With  increasing  concentration  of  the  added 
salt,  they  observed  a  marked  increase  in  viscosity  "  with  a  strong 
tendency  to  jelly."  In  a  later  study3  they  verify  this  finding 
for  the  ammonium  soap  of  palm  kernel  oil  when  various  hydroxids 
or  salts  are  added  to  it.  Recently  G.  H.  A.  .CLOWES  4  has  cor- 
roborated these  general  findings  for  sodium  oleate.  He  writes: 

"Na  oleate  was  treated  with  salt  at  different  concentrations,  and  it 
was  found  that  at  .4  to  .45M  NaCl  complete  precipitation  of  the  soap 
took  place.  It  was  noted,  however,  that  prior  to  precipitation  a  tendency 
to  jelly  formation  was  exhibited  in  the  zone  from  .2M  NaCl  to  .4  or 
.45M  NaCl.  .  .  .  Further  tests  using  varying  proportions  of  soap,  vary- 
ing proportions  of  NaOH,  and  of  NaCl  and  other  salts  of  Na  brought 
out  the  remarkable  fact  that  as  long  as  the  soap  employed  was  not  too 
greatly  diluted  and  was  slightly  alkaline,  a  jelly  would  be  formed  at  all 
points  between  .2M  Na  and  .45M  Na,  regardless  of  whether  the  Na 
was  derived  from  NaOH,  from  NaCl  or  other  salts  of  Na." 

The  explanations  which  the  various  authors  offer  of  the  phe- 
nomena observed — if  they  make  the  attempt  at  all — are  for  the 
most  part  extremely  complicated.  We  confess  to  large  inability 
at  times  to  understand  just  what  they  mean,  for  not  only  do  the 
different  authors  contradict  each  other  but  their  individual  con- 
cepts are  often  self-contradictory.  As  well  as  we  can  understand 
them,  their  views  are  about  as  follows : 

HOFMEISTER  does  not  attempt  to  account  for  the  jelly  for- 
mation at  all,  but  considers  the  separation  of  the  soap  from  the 
aqueous  dispersion  medium  as  due  to  the  "  water-attracting 
power  "  of  the  added  salt.  The  soap,  he  holds,  is  deprived  of 
its  solvent  because  the  added  salt  combines  with  the  solvent. 
This  notion  of  HOFMEISTER  has  been  much  disparaged,  but  we 

1  J.  W.  McBxiN  and  MILLICENT  TAYLOR:  Zeitschr.  f.  physik.  Chem.,  76, 
179  (1911). 

2F.  GOLDSCHMIDT  and  L.  WEISSMANN:  Zeitschr.  f.  Elektrochem.,  18,  380 
(1912). 

8  F.  GOLDSCHMIDT  and  L.  WEISSMANN:  Kolloid-Zeitschr.,  12,  18  (1913). 

4  G.  H.  A.  CLOWES:  Proc.  Soc.  Exp.  Biol.  and  Med.,  13,  114  (1916). 


112  SOAPS  AND- PROTEINS 

are  of  the  opinion  that  such  a  change  does  occur  and  that  it  is 
partly  responsible  for  the  phenomena  observed  in  these  colloid 
systems. 

BOTAZZI  and  VICTOROW  hold  that  the  addition  of  alkali  to 
their  dialyzed,  "  acid  soap  "  leads  to  the  formation  of  neutral 
soap  "  which  splits  hydrolytically.  The  molecules  polymerize 
with  the  formation  a  true  colloid  solution  containing  micellae  and 
'  colloid  ions/  which  then  lead  to  an  increase  in  viscosity  because 
the  water  of  the  system  is  held  more  firmly  through  hydration 
or  imbibition." 

McBAiN  and  TAYLOR,1  while  originally  insistent  that  their 
studies  "  undoubtedly  prove,  in  opposition  to  the  view  of  KRAFFT, 
that  the  normal  soaps  in  concentrated  solution  are  not  colloids," 
conclude  later,2  and  more  correctly  we  think,  when  working  with 
sodium  palmitate  (at  90°)  in  the  presence  of  sodium  hydroxid, 
that  they  have  in  hand  systems  "  in  reversible  equilibrium  con- 
sisting of  electrolyte,  hydrosol  and  coagulum."  The  increase  in 
colloidality  observed  in  their  studies  they  attribute,  in  the  main, 
to  the  formation  of  "  acid  palmitate." 

GOLDSCHMIDT  and  WEISSMANN  hold  that  a  satisfactory  expla- 
nation of  the  changes  in  the  viscosity  of  their  soap  under  the  influ- 
ence of  alkalies  and  salts  is  still  a  matter  of  the  future.  They 
emphasize  as  factors  of  possible  worth  changes  in  the  hydrolytic 
cleavage  of  the  soap  and  the  formation  of  acid  soap,  though  how 
such  factors  act  they  do  not  say. 

CLOWES'  hypothesis  reads  as  follows: 

"A  dispersion  of  Na  oleate  in  water  represents  a  dispersion  of  particles 
of  oleic  acid  by  means  of  NaOH.  Further  additions  of  NaOH  lead  to  a 
more  perfect  dispersion  of  the  soap  particles,  owing  to  the  fact  that  the 
OH  ion  is  more  readily  adsorbed  than  the  Na  ion.  NaCl  exerts  a  similar 
effect  to  NaOH,  the  Cl  ions  exerting  a  dispersing  effect  analogous  to  that 
of  the  OH  ions,  but  since  they  are  far  less  readily  adsorbed  than  the 
OH  ions  their  effect  is  considerably  smaller.  .  .  .  The  soap  particles 
possess  a  negative  charge  attributable  presumably  to  adsorbed  anions. 
This  charge  prevents  their  coalescence  until  the  concentration  of  the 
Na  ions  reaches  such  a  point  that  they  also  come  into  play  and  by  adsorp- 
tion on  the  particles  tend  to  counteract  or  diminish  the  negative  charge 
conveyed  by  the  previously  adsorbed  OH  or  Cl  ions.  When  a  certain 

1  J.  W.  McBAm  and  MILLICENT  TAYLOR:  Ber.  d.  deut.  chem.  Gesell.,  48, 
321  (1910). 

2  J   W.  McBAiN  and  MILLICENT  TAYLOR:  Zeitschr.  f.  physik.  Chem.,  76 
179  (1911). 


THE  COLLOID-CHEMISTRY  OF  SOAPS  113 

concentration  of  the  cation  is  reached  a  critical  zone  commences  in  which 
jelly  formation  or  precipitation  appears  to  depend  entirely  upon  the  rela- 
tive proportions  of  adsorbed  cations  and  anions.  If  at  the  commence- 
ment of  this  critical  zone  the  residual  negative  charge  ...  is  sufficient 
to  maintain  a'perfect  dispersion  .  .  .  jelly  formation  will  ensue  at  higher 
concentrations.  If  this  residual  negative  charge  ...  is  insufficient  .  .  . 
if  agglutination,  aggregation  and  sedimentation  under  the  influence  of 
gravity  has  already  commenced,  precipitation  necessarily  ensues  at 
higher  concentrations.  ...  If  at  the  critical  point  the  sum  total  of 
adsorbed  anions  is  not  sufficiently  in  excess  of  that  of  adsorbed  cations  to 
insure  perfect  dispersion,  precipitation  instead  of  jelly  formation  ensues. 
This  explains  the  necessity  for  a  certain  minimum  concentration  of  NaOH 
with  its  readily  adsorbed  OH  ions  to  insure  jelly  formation  in  the  case 
cited  above." 


The  contradictory  nature  of  the  explanations  here  reviewed 
is  self-evident.  To  secure  the  proper  results  CLOWES  holds  that 
the  soap  must  be  "  alkaline  to  phenolphthalein."  Our  own  soap, 
which  in  practice  worked  quite  like  his,  was  prepared  by  adding 
to  each  other  the  chemically  equivalent  weights  of  fatty  acid 
and  alkali  necessary  to  yield  a  "  neutral  "  soap.  In  the  concen- 
trations in  which  we  employed  our  stock  soap  it  was  not  alkaline 
to  phenolphthalein.  The  same  kind  of  soap  stock  or  one  more 
decidedly  "  acid  "  was  employed  by  all  the  other  students  in 
this  field.  In  fact,  it  would  seem  that,  with  the  exception  of 
CLOWES,  the  majority  of  observers  had  inclined  to  the  belief  that  an 
overplus  of  acid  in  their  soap  systems  was  necesssary  for  an  under- 
standing of  the  viscosity  changes.  Nevertheless,  and  independ- 
ently of  all  hypothesis,  there  is  reported  throughout  the  experi- 
ments of  all  these  workers  (including  our  own)  the  same  sequence 
of  observed  facts  which  has  been  set  down  in  detail  in  the  pre- 
ceding pages,  namely,  an  initial  increase  in  viscosity  resulting 
ultimately  (when  the  soap  system  is  not  too  dilute)  in  gelation, 
followed  by  a  decrease  in  viscosity  and  a  gradually  increasing 
dehydration  and  complete  separation  of  the  soap. 

c.  On  the  Theory  of  the  "  Salting-out  "  of  Soaps.  .We  refrain 
from  a  detailed  criticism  of  the  views  of  these  authors.  It  is 
self -apparent  how  all  too  one-sided  notions  of  jelly  formation  in 
soaps  (like  the  electrical)  must  come  to  grief  as  soon  as  it  is  remem- 
bered that  such  jellies  may  be  produced  from  non-aqueous  solvents 
and  anhydrous  soaps  and  under  circumstances  which  allow  of 
none  of  the  orthodox  conditions  deemed  necessary  for  the  develop- 


114 


SOAPS  AND  PROTEINS 


o 

I 

o 


ment  of  electrolytic  disso- 
ciation.1 The  importance 
of  "  alkalinity  "  or  of  "  hy- 
droxyl  ions  "  disappears  when 
ammonium  hydroxid  is  found 
incapable  of  doing  what  po- 
tassium hydroxid  or  potas- 
sium chlorid  does;  the  "  al- 
kaline," "  neutral"  or  "  acid  " 
character  of  the  original  soap 
stock  can  hardly  be  of  funda- 
mental importance  when  all 
three  are  seen  to  exhibit  the 
same  general  behavior  to- 
ward added  substances. 

If  we  attempt  to  explain 
the  successive  changes  which 
follow  the  addition  of  fixed 
alkali  or  a  neutral  salt  to 
potassium  oleate  (or  any 
similar  soap),  and  try  to  do 
this  without  recourse  to  too 
many  or  too  violent  assump- 
tions, the  following  seems  the 
simplest  way  out. 

The  entire  series  of  changes 
observed  in  the  salting-out  of 
a  soap  by  an  alkali  or  a  salt 
is  readily  understood  if  it  is 
assumed  that  the  added  neutral 
salt  or  alkali  hydroxid  unites 
with  the  solvent  to  form  a 
hydrate  or  solvate  and  that  the 
consequent  viscosity  changes 
(including  gelation)  are  de- 
pendent upon  the  changes  in 
viscosity  observed  whenever  one 
liquid  is  emulsified  in  a  second. 


1  See  the  preceding  sections  (pages  30  to  77)  on  soap/alcohol  and  soap/z 
systems. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  115 

It  does  not  matter  for  our  purposes  whether  such  union  with 
the  "  solvent  "  is  brought  about  by  the  molecules  or  the  ions  or 
any  other  derivatives  of  the  salt.  The  solvaies  (hydrates)  after  being 
formed  then  separate  out  in  dispersed  form  in  the  potassium  oleate. 

Diagrammatically  the  successive  changes  are  illustrated  in 
Fig.  74.  If,  to  simplify  matters,  we  represent  the  original  pure 
potassium  oleate  solution  as  a  homogeneous  system  l  as  indicated 
in  tube  A  of  Fig.  74,  the  effect  of  adding  some  molecules  of  fixed 
alkali  or  salt  may  be  represented  by  the  diagram  marked  B. 
Hydration  of  the  salt  molecules  has  two  effects:  (1)  It  with- 
draws water  from  the  original  potassium  system  and  thus  through 
increase  in  the  concentration  of  the  potassium  oleate  tends  to 
stiffen  the  system.  But  this  effect  is  probably  not  large  as  com- 
pared with  (2)  the  effects  upon  viscosity  of  the  dispersion  of  one 
material  in  a  second.  The  increase  in  viscosity  due  to  such  sub- 
division of  one  material  in  a  second  is  observed  under  widely 
varying  circumstances.  A  good  example  for  our  purposes  is  that 
represented  by  the  increase  in  viscosity  when  one  liquid  (like 
cottonseed  oil)  is  emulsified  in  a  second  (like  a  soap  solution). 
The  "  mayonnaise  "  which  results  may  become  so  stiff  that  it 
will  stand  alone.  But  the  same  type  of  change  is  observed  when 
a  dry  sand  (which  "  flows  "  readily)  is  mixed  with  a  little  water 
and  a  mass  results  that  can  be  molded.  Even  a  gas  subdivided 
into  a  liquid  will  yield  such  "  solid  "  structures  as  when  air  is 
beaten  into  a  liquid  white  of  egg  to  yield  a  "  foam." 

The  viscosity  of  such  diphasic  systems — and  it  is  well  to  bear 
in  mind,  in  the  case  of  the  soaps,  more  particularly  diphasic 
systems  consisting  of  one  liquid  dispersed  in  a  second  or  of  a 
solid  dispersed  in  a  liquid — increases  with  every  increase  in  the 
concentration  of  the  internal  dispersed  phase  and  with  every 
decrease  in  the  size  of  the  individual  dispersed  particles.  The 
viscosity  of  an  emulsion  of  liquid  oil  in  liquid  soap,  for  instance, 
increases  as  more  and  more  oil  is  beaten  into  the  soap;  on  the 
other  hand,  with  a  given  amount  of  oil  subdivided  into  a  given 
volume  of  soap  the  viscosity  of  the  mixture  is  increased  if  the 
previously  coarse  emulsion  is  made  finer  by  "  homogenizing."  2 

1  It  is  at  least  a  diphasic  system  as  emphasized  on  page  69,  but  for  our 
purposes  we  will  call  it  a  monophasic  one. 

2  For  references  to  the  literature  and  specific  studies  of  the  emulsions  see 
MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Science,  43,  468  (1916);  Fata 
and  Fatty  Degeneration,  New  York  (1917). 


116  SOAPS  AND  PROTEINS 

* 

It  is  such  increase  in  the  number  of  hydrated  salt  particles 
with  increasing  concentration  of  the  added  salt  that  explains 
the  progressive  increase  in  the  viscosity  (see  diagram  C)  which, 
when  the  amount  of  water  in  the  system  is  not  too  high,  culmi- 
nates in  gelation.  If  the  concentration  of  the  salt  is  still  further 
increased,  the  tune  approaches  when  the  number  or  size  of  the 
hydrated  salt  particles  becomes  so  great  that  they  touch  each 
other  (diagram  D).  When  this  happens  a  critical  point  has 
been  reached  and  there  must  appear  a  change  in  the  system,  for 
the  hydrated  salt  particles  now  become  the  continuous  external 
phase  while  the  soap  particles  form  the  internal  divided  phase. 
Such  change  in  type  of  emulsion  even  without  change  in  the 
quantitative  relationship  of  the  two  liquids  composing  the  emul- 
sion is  regularly  followed  by  a  change  in  viscosity.  This  situation 
is  indicated  in  tube  E  of  Fig.  74.  The  viscosity  of  the  system 
now  tends  in  the  direction  of  the  salt  solution  and  so,  with  pro- 
gressive additions  of  salt,  falls.  This  is  the  region  of  secondary 
liquefaction  after  the  region  of  gelation  in  our  experiments.  At 
this  point,  however,  the  soap  system  also  shows  the  first  evidences 
of  becoming  turbid.  This  is  because  more  and  more  water  has 
been  taken  from  the  soap  and  as  this  becomes  dehydrated  its 
index  of  refraction  changes.  Being  different  from  that  of  the 
dispersion  medium  the  mixture  appears  milky.  The  dehydrated 
soap  particles,  being  possessed  of  a  lower  specific  gravity  than 
that  of  the  alkaline  solution  or  salt  solution  constituting  the 
dispersion  medium,  now  begin  to  float  to  the  top  as  indicated 
over  F  in  Fig.  74.  When  enough  salt  has  been  added  to  the 
system,  the  soap  is  entirely  dehydrated,  as  shown  in  diagram  G?.1 

3.  On  the  "Salting-out"  of  Different  Soaps 

The  preceding  pages  have  made  clear  the  general  laws  which 
underlie  the  salting-out  of  a  soap  by  different  salts.  We  have 
now  to  consider  the  question  of  how  different  soaps  behave  when 
subjected  to  the  salting-out  effects  of  a  single  salt. 

1  It  is  self-evident  that  what  has  been  here  written  of  the  salting-out 
process  as  observed  in  soap  manufacture  holds  with  equal  force  for  the  salting- 
out  processes  of  many  other  technological  procedures  as  in  aniline  dye,  cheese, 
and  butter  manufacture.  For  the  application  of  these  principles  to  certain 
phenomena  of  "coagulation"  as  observed  in  milk,  blood,  muscle  juice,  etc., 
see  page  233. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  117 

There  have  been  many  studies  made  of  this  question,  but  for 
the  most  part  they  refer  to  the  salting-out  of  mixed  soaps  as 
obtained  from  different  mixed  fats.  Under  such  circumstances 
we  are  obviously  dealing  with  the  salting-out  of  a  series  of  soaps.1 
We  have  been  able  to  find  only  a  single  statement  covering  the 
salting-out  of  different  pure  soaps  by  a  single  salt.  C.  STIEPEL  2 
examined  the  behavior  of  the  sodium  soaps  of  caproic,  heptylic, 
caprylic,  pelargonic,  capric,  lauric,  myristic,  palmitic  and  stearic 
acids  towards  solutions  of  common  salt.  While  sodium  caproate 


SALTING    OUT    OF  SOAPS 
OF  THE   ACETIC    SERIES 

PALM.TATE-C.U-Bi  BY   SODIUM    CHL°RID 


MYRI  STATE- C14 
LAURATE  —  C1Z 
CAPRATE—  C10 


CAPRYLATE-C8 


NO   SEPARATION 


0-»««.«,<».|M  ZM  3M  4M  5M  6M- SAT 

FIGURE  75. 

was  not  salted  out  by  a  saturated  solution  of  sodium  chlorid, 
and  the  succeeding  four  soaps  remained  gelatinous,  the  laurate, 
myristate,  palmitate  and  stearate  proved  "  insoluble  "  successively 
in  17.7  percent  (3.02  molar),  9.03  percent  (1.54  molar),  6.94 
percent  (1.19  molar)  and  4.92  percent  (0.84  molar)  solutions  of 
sodium  chlorid. 

These  values  have  been  verified  by  R.  J.  KRONACHER,S  whose 
findings  for  a  series  of  sodium  salts  are  reproduced  in  Fig.  75. 

1  See  for  example,  J.  LEIMDORFER:   Technologic  der  Seife,  1,  14,  Dresden 
(1911). 

2  C.  STIEPEL:  Weyl's  Einzelschriften  z.  chem.  Tech.,  1,  348,  Leipzig  (1911). 
a  R.  J.  KRONACHER:  Personal  communication  (1920). 


118  SOAPS  AND  PROTEINS 

Molar  equivalents  of  the  different  sodium  soaps  (1/10  mol)  were 
dissolved  in  equal  volumes  of  water  (1000  cc.)  and  the  whole 
brought  into  homogeneous  solution  at  the  temperature  of  a  boiling 
water  bath.  Enough  salt  was  then  added  at  the  high  temperature 
so  that  on  cooling  the  mixture  to  18°  C.  a  first  separation  from 
the  pure  dispersion  medium  (salt  water)  was  observed.  It  will 
be  noticed  that  as  the  acetic  series  is  ascended,  a  lower  and  lower 
concentration  of  sodium  chlorid  is  required  to  bring  about  such 
separation.  While  in  the  concentrations  of  soap  employed, 
sodium  caprylate  did  not  come  out  in  even  a  saturated  (over 
5  molar)  sodium  chlorid  solution,  sodium  stearate  separated  from 
the  dispersion  medium  when  less  than  a  1  molar  sodium  chlorid 
concentration  prevailed. 

A  second  series  of  experiments  to  illustrate  these  general 
truths  is  presented  in  Table  LV  and  Fig.  76.  While  the  arrange- 
ment in  these  experiments  is  intended  for  use  under  another 
heading  later,  the  findings  fit  in  at  this  point.  The  experiments 
show  the  effects  of  adding  the  same  volumes  of  increasingly  con- 
centrated sodium  hydroxid  solution  to  equimolar  amounts  of 
the  different  fatty  acids  of  the  acetic  series,  only  those  members 
being  used  in  which  soap  formation  takes  place  at  ordinary  room 
temperature.  (Soap  is  produced,  in  other  words,  by  the  so-called 
cold  process.) 

Fig.  76  and  Table  LV  show  that  only  clear  solutions  are 
obtained  in  the  case  of  formic  and  acetic  acids.  At  the  same 
molar  concentration,  sodium  propionate  begins  to  be  salted 
out  in  the  higher  concentrations  of  the  sodium  hydroxid.  As 
we  pass  to  the  sodium  butyrate,  sodium  valerate,  sodium  caproate, 
sodium  caprylate,  sodium  caprate  and  sodium  laurate,  the  salting- 
out  effect  moves  little  by  little  to  the  left.  The  experiment 
again  shows  therefore  that  a  soap  of  the  acetic  series  is  salted  out 
with  increasing  ease  (by  sodium  hydroxid,  in  this  instance)  as  we 
ascend  the  series. 

Fig.  76  and  Table  LV  illustrate,  however,  a  second  point  pre- 
viously commented  upon.  It  will  be  observed  that  beginning 
with  sodium  butyrate  and  going  up  in  the  chemical  series  one  or 
more  tubes  are  filled  with  solid  gels.  This  is  because,  as  we  ascend 
the  series,  soaps  of  an  increasing  gelation  capacity  are  produced. 
The  final  picture  seen  in  the  photograph  is  therefore  the 
composite  represented  by  (a)  the  production  of  soaps  possessed 


THE  COLLOID-CHEMISTRY  OF  SOAPS  119 


WH\ 


W/////M/MM 


'f't't'ii  i't  i  rf 


W/fl/lllh 


FIGURE  76. 


120 


SOAPS  AND  PROTEINS 


by  themselves  of  an  increasing  gelation  capacity  and  (6)  of  an 
increased  sensitiveness  to  the  salting-out  effect  by  an  excess  of 
sodium  hydroxid. 

TABLE   XXVI 
POTASSIUM  OLEATE — Potassium  Hydroxid 


Concentration  of  mixture. 

Remarks. 

(1)  5  cc.  pot 

assium  oleate+9  cc.  H2O  +  1  cc.  5  n  KOH 

Liquid 

(2)   See. 

"     +8cc.     "    -1-2  cc.    "       " 

Liquid 

(3)   5cc. 

"     +7cc.     "    +3oc.   " 

Gel 

(4)   5cc. 

"     +  6cc.     "    -|-4  cc.    " 

Gel 

(5)   5  cc. 

"     +5cc.     "    +5cc.    " 

Beginning  dehydration  and  sepa- 

ration 

(6)   5  cc. 

"      +4cc.     "    +6cc.    " 

Increasing  dehydration  and  sepa- 

ration 

(7)   OCP. 

"     +3cc.     "    +7cc.    " 

Increasing  dehydration  and  sepa- 

ration 

(8)   5cc. 

"      +2cc.     "    -|-8  cc.    " 

Increasing  dehydration  and  sepa- 

ration 

(9)   5  cc. 

"      -f  1  cc.     "    +9cc.    " 

Increasing  dehydration  and  sepa- 

ration 

(10)  See. 

"     -1-lOcc.  5n  KOH 

Great   dehydration   and    separa- 

tion 

(11)   Sec. 

"      +10  cc.  H»O  (control) 

Mobile  liquid 

TABLE   XXVII 

POTASSIUM  OLEATE — Sodium  Hydroxid 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium  oleate  +9 . 5  cc.  HiO  -f  0 . 5  cc.  5  n  NaOH 

(2)  5cc.          "  "      -1-9      cc.    "    +1      cc.  " 

(3)  occ.          "  "      +  8      cc.    "    +2      cc.  "        " 

(4)  5cc.         "  "      +7      cc.    "    +3      cc.  " 


(5)  5cc. 

(6)  5cc. 

(7)  5cc. 

(8)  5cc. 


+6      cc.    "    -|-4      cc.  " 
"      -|-5      cc.    "    +5      cc.  " 
"      4-lOcc.  5n  NaOH 
11      -f  10  cc.  H*O  (control) 


Liquid 

Liquid 

Gel 

Beginning  dehydration  and  sepa- 
ration 

Increasing  dehydration  and  sepa- 
ration 

Increasing  dehydration  and  sepa- 
ration 

Great  dehydration  and  separa- 
tion 

Mobile  liquid 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


121 


TABLE   XXVIII 
POTASSIUM  OLE  ATE — Ammonium  Hydroxid 


Concentration  of  mixture. 

Remarks. 

(1)   5cc. 

potassium  oleate+9  cc.  HiO  +  1  cc.  5  n  NH4OH 

Mobile  liquid 

(2)   5cc. 

"     +8cc.     "    +2  cc.    " 

Mobile  liquid 

(3)   5cc. 

"     +7  cc.     "    +3  cc.    " 

Mobile  liquid 

(4)   5cc. 

"     +6  cc.     "    +4  cc.   " 

Mobile  liquid 

(5)   5cc. 

"     +5  cc.     "    +5  cc.   "         " 

Mobile  liquid 

(6)   5cc. 

"     +4  cc.     "    +6cc.   " 

Mobile  liquid 

(7)   5  cc. 

"     +3  cc,     "    +7  cc.    " 

Mobile  liquid 

(8)   5cc. 

"     +2  cc.     "    +8cc.   " 

Mobile  liquid 

(9)   See. 

"     +1  cc.     "    +9cc.   " 

Mobile  liquid 

(10)   5cc. 

"     +  10cc.  5nNH4OH 

Mobile  liquid 

(11)  5cc. 

"     +10cc.  HiO  (control) 

Mobile  liquid 

TABLE   XXIX 
POTASSIUM  OLEATE — Potassium  Fluorid 


Concentration  of  mixture. 


Remarks. 


(1)  5cc. 

potassium  oleate+9  cc.  HjO  +  1  cc.  2  m  KF 

Mobile  liquid 

(2)   5  cc. 

"     +8  cc.     "    +2  cc.     "      " 

Slightly  viscid 

(3)   5  cc. 

"     +7  cc.     "    +3  cc.    "      " 

Stiff  gel 

(4)   5  cc. 

"     +6  cc.     "    +4  cc.    " 

Stiffest  gel 

(5)   5  cc. 

"     +5  cc.     "    +5  cc.     ' 

Viscid,  faintly  turbid 

(6)   5  cc. 

"     +  4  cc.     "    +6  cc.     "      " 

Slightly  viscid,  turbid 

(7)   5  cc. 

"     +3  cc.     "    +7  cc.    "      " 

Mobile,  turbid 

(8)   5  cc. 

"     +2  cc.     "    +8  cc.    " 

Mobile,  turbid 

(9)   5  cc. 

"     +1  cc.     "    +9  cc.     "      " 

Mobile,  turbid,  beginning  dehy- 

dration 

(10)   5cc. 

"     4-10  cc.  2  m  KF 

Mobile,  increasing  dehydration 

(11)   5cc. 

"     +  10  cc.  HiO  (control) 

Mobile  liquid 

122 


SOAPS  AND  PROTEINS 


TABLE   XXX 

POTASSIUM  OLEATE — Potassium  Chlorid 


Concentration  of  mixture. 


Remarks. 


(1)  See. 

potassium  oleate+9  cc.  HtO  +  1  cc.  2  m  KC1 

Mobile  liquid 

(2)   5cc. 

,, 

+8  cc. 

"    +  2cc.    ' 

Viscid 

(3)  5cc. 

>  1                                  .41 

+7cc. 

"    +3cc.    "       " 

Stiff  gel 

(4)  5cc. 

,, 

+6cc. 

"    +4cc.    "       " 

Stiffest  gel 

(5)  Sec. 

4.                                    1. 

+5cc. 

"    +5cc.    "       " 

Stiff  gel 

(6)  5cc. 

4. 

+4  cc. 

"    +6  cc.    "       " 

Viscid 

(7)  See. 

4. 

+3  cc. 

"    +7  cc.    "      " 

Less  viscid,  slightly  turbid 

(8)  5cc. 

4. 

+2  cc. 

"    +8cc.    "       " 

Mobile,  turbid 

(9)  5cc. 

4. 

+  lcc. 

"    +9  cc.    "       " 

Mobile,  turbid 

(10)   5  PC 

44                                    44 

+  10  cc. 

2  m  KC1 

Mobile,  turbid,  beginning  dehy- 

dration 

(11)  5cc. 

-1-lOcc. 

HjO  (control) 

Mobile  liquid 

TABLE   XXXI 

POTASSIUM  OLEATE — Potassium  Bromid 


Concentration  of  mixture. 


Remarks. 


(1)   5  cc.  potassium 

oleate  +  6  .  0  cc.  HiO  +4  .  0  cc.  2  m  KBr 

Stiff  gel 

(2)   5cc. 

"     +5.  Occ.     "    +5.  Occ.    "       " 

Stiffest  gel 

(3)   occ. 

"     +4.  Occ.     "    +6.  Occ.    "       " 

Less  stiff  gel 

(4)   5cc. 

"     +3.5cc.     "    +6.5cc.    " 

Less  stiff  gel 

(5)   5cc. 

"     +3.  Occ.     "    +7.  Occ.    "       " 

Markedly  less  stiff 

(6)   5  cc. 

"     +2.5cc.     "    +7.5cc.    "       " 

Markedly  less  stiff 

(7)   5cc. 

"     +2.  Occ.     "    +8.  Occ.    "       " 

Markedly  less  stiff 

(8)   5  cc. 

"      +  1.5cc.     "    +8.5cc.    "       " 

Markedly  less  stiff 

(9)    5cc. 

"     +1.0cc.     "    +9.  Occ.    "       " 

Beginning  dehydration 

(10)    5cc. 

"     +0.5cc.     "    +9.  See.    "       " 

Increasing  dehydration 

(11)   5cc. 

"     +  10cc.  2  m  KBr 

Marked  dehydration 

(12)   5  cc. 

"     +10  cc.  H»O  (control) 

Mobile  liquid 

TABLE   XXXII 

POTASSIUM  OLEATE — Potassium  lodid 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium  oleate  +  8  cc.  HsO  +  2  cc.  2  m  KI 

(2)  Sec.  "  "  +7cc.     "    +3cc.    "     " 

(3)  5cc.  "  "  +6cc. 

(4)  See.  +5cc. 

(5)  5  cc.  "  "  +4  cc. 

(6)  5cc.  "  "  +3cc. 

(7)  5  cc.  "  "  +2  cc. 

(8)  5cc.  "  "  +1  cc. 

(9)  5cc. 
(10)  5  cc. 


+4  cc.  ' 

+  5cc.  " 

+  6cc.  " 

+  7cc.  " 

+  8cc.  " 

+9cc.  " 

+  10  cc.  2  m  KI 

+  10  cc.  HiO  (control) 


Slightly  viscid 

Stiff  gel 

Stiffest  gel 

Stiff  gel 

Viscid 

Slightly  viscid 

Slightly  viscid 

Beginning  dehydration 

IIH  [rasing  dehydration 

Mobile  liquid 


THE  COLLOID-CHEMISTRY  OF  SOAPS 

TABLE   XXXIII 

POTASSIUM  OLEATE — Potassium  Nitrate 


123 


Concentration  of  mixture. 

Remarks. 

(1)   5cc. 

potassium  oleate4-9  cc.  HiO  +  1  cc.  m  KNOj 

Mobile  liquid 

(2)  5cc. 

"     -f-8  cc.    "    +2  cc.  " 

Mobile  liquid 

(3)  5  cc. 

"     +7  cc.    "    4-3cc.  "      " 

Liquid 

(4)  5cc. 

"     +6  cc.     "    +4cc.  "      " 

Increasing  viscidity 

(5)  5cc. 

"     -f-5  cc.     "    4-5  cc.  " 

Increasing  viscidity 

(6)  5cc. 

"     4-4  cc.     "    +6  cc.  " 

Increasing  viscidity 

(7)  5  co. 

"     4-3  cc.     "    4-7  cc.  "      " 

Increasing  viscidity 

(8)  5cc. 

41     4-2  cc.     "    4-8  cc.  "      " 

Increasing  viscidity 

(9)   5cc. 

"     4-1  cc.     "    4-9  cc.  "      " 

Gel 

(10)  5cc. 

"     4-lOcc.  m  KNOj 

Gel 

(11)  5cc. 

"              "     4-10  cc.  HzO  (control) 

Mobile  liquid 

TABLE   XXXIV 

POTASSIUM  OLEATE  —  Potassium  Nitrate 

Concentration  of  mixture. 

Remarks 

(1)   5  cc.  potassium  oleate+9  cc.  HiO  +  1  cc.  4  m  KNOj 

Mobile 

(2)   See. 

'     4-8  cc.     "    4-2  cc.    ' 

Gel 

(3)   5cc. 

"     4-7  cc.     "    4-3  cc.    " 

Stiff  gel 

(4)   5cc. 

"     4-6  cc.     "    4-4  cc.    " 

Stiff  gel 

(5)  5cc. 

"     4-5  cc.     "    4-5  cc.    " 

Viscid 

(6)   5  cc. 

"     4-4  cc.     "    4-6  cc.    " 

Viscid 

(7)  5  cc. 

"     4-3  cc.     "    4-7  cc.    " 

Less  viscid 

(8)   5  cc. 

"     4-2  cc.    •"    4-8  cc.    "       •" 

Less  viscid 

(9)   5cc. 

"     4-1  cc.    "    4-9  cc.    " 

Less     viscid;     crystallization    of 

KNOj 

(10)   5cc. 

"      4-10  cc.  4  m  KNOj 

Less     v  scid  ;     crystallization    of 

KNOj 

(11)   S  co 

"      4-10  cc.  HjO  (control) 

Mobile  liquid 

TABLE   XXXV 

POTASSIUM  OLEATE  —  Potassium  Sulphocyanate 

Concentration  of  mixture. 

Remarks. 

(1)   5cc. 

potassium  oleate  4-9  cc.  HiO4-l  cc.  m  KCNS 

Mobile  liquid 

(2)   5cc. 

"      4-8  cc.     "    4-2  cc.  "       " 

Mobile  liquid 

(3)   5cc. 

"      4-7  cc.     "    4-3  cc.  "      " 

Increasing  viscidity 

(4)    occ. 

"     4-6  cc.     "    4-4  cc.  "      " 

Increasing  viscidity 

(5)    5  cc. 

4-5  cc.     "    4-5  cc.  " 

Increasing  viscidity 

(6)    5cc. 

"     4-4  cc.     "    4-6  cc.  "      " 

Increasing  viscidity 

(7)   5cc. 

"     4-3  cc.     "    4-7  cc.  "      " 

Gel 

(8)   5cc. 

"     4-2  cc.     "    4-8  cc.  "      " 

Stiff  gel 

(9)   5cc. 

"     4-1  cc.     "    4-9  cc.  "      " 

Stiff  gel 

(10)  See. 

"     4-10cc.  m  KCNS 

Stiff  gel 

(11)  5cc. 

"     4-10  cc.  HiO  (control) 

Mobile  liquid 

124 


SOAPS  AND  PROTEINS 


TABLE   XXXVI 

POTASSIUM  OLEATE — Potassium  Sulphocyanate 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium 

oleate  +6  .  0  cc.  HjO  +4  .  0  cc.  2  m  KCNS   Stiff  gel 

(2)   5cc. 

"     +5.0cc.    "    +5.  Occ.   " 

Stiff  gel 

(3)   Sec. 

"      +4.0cc.    "    +6.  Occ.  " 

Less  stiff  gel 

(4)  5cc. 

"      +3.5cc.    "    +  6.5cc.  " 

Less  stiff  gel 

(5)   5cc. 

"      +3.0cc.    "    +7.0cc.  " 

Viscid  liquid 

(6)   5cc. 

"      +2.5cc.    "    +  7.5cc.   " 

Viscid  liquid 

(7)   5cc. 

"      +2.0cc.    "    +8.0cc.   " 

Liquid 

(8)   5cc. 

"      +1.5  cc.    "    +8.5cc.   " 

Liquid 

(9)   5cc. 

"      +  1.0ce.    "  .-(-9.  Occ.  " 

Liquid 

(10)    5cc. 

"      +0.5cc.    "    -1-9.  5  cc.   " 

Liquid 

(11)   See. 

"      +10  cc.  2m  KCNS 

Liquid 

(12)  5cc. 

"      +10cc.  H2O 

Mobile  liquid 

TABLE   XXXVII 
POTASSIUM  OLEATE — Potassium  Sulphocyanate 


Concentration  of  mixture. 


Remarks. 


(1)  5 cc.  potassium oleate  + 6. Occ.  H2O+4.0cc.4m  KCNS 

(2)  5cc.          "  "      +5. Occ.    "    +5. Occ.   " 

(3)  5cc.          "  "      +4. Occ.    "    +6. Occ.   " 

(4)  5cc.          "  "      +3.5cc.    "    +6.5cc.   " 

(5)  5cc.         "  "      +3. Occ.    "    +7. Occ.   " 


(6)  5cc.         "  "      +2.5cc.    "    +7. See. 


(7)  5cc. 


(8)  5cc. 


(9)  5cc. 


(10)  5cc. 


(11)  5cc. 


(12)  See. 


+2. Occ.    "    +8. Occ. 


"      +1.5cc.    "    +8.5cc. 


"      +1.0cc.    "    +9. Occ. 


"      +0.5cc.    "    +9.5cc. 


"      +10  cc.  4m  KCNS 


"      + 10  cc.  H»O  (-control) 


Turbid,  liquid 

Turbid,  liquid 

Turbid,  liquid 

Beginning  dehydration 

Increasing  dehydration  with 
decrease  in  amount  of  soap  gel 
and  increase  in  collar  of  dehy- 
drated soap 

Increasing  dehydration  with 
decrease  in  amount  of  soap 
gel  and  increase  in  collar  of 
dehydrated  soap 

Increasing  dehydration  with 
decrease  in  amount  of  soap 
gel  and  increase  in  collar  of 
dehydrated  soap 

Increasing  dehydration  with 
decrease  in  amount  of  soap  gel 
and  increase  in  collar  of  dehy- 
drated soap 

Increasing  dehydration  with 
decrease  in  amount  of  soap  gel 
and  increase  in  collar  of  dehy- 
drated soap 

Increasing  dehydration  with 
decrease  in  amount  of  soap  gel 
and  increase  in  collar  of  dehy- 
drated soap 

Increasing  dehydration  with 
decrease  in  amount  of  soap  gel 
and  increase  in  collar  of  dehy- 
dration soap 

Mobile  liquid 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


125 


TABLE   XXXVIII 
POTASSIUM  OLE  ATE — Potassium  Acetate 


Concentration  of  mixture. 

Remarks. 

(1)   5  cc. 

potassium  oleate+9  cc.  HjO  +  1  cc.  m  KCiHaOi 

Mobile  liquid 

(2)   See. 

44     +8cc.    "    -f-2  cc.  " 

Mobile  liquid 

(3)   See. 

"     4-7  cc.    "    +3cc.  " 

Viscid,  slightly  turbid 

(4)   5cc. 

"     4-6  cc.    "    +4  cc.  " 

More  viscid  and  turbid 

(5)   5cc. 

"     4-5  cc.    "    +5  cc." 

Soft,  turbid  gel 

(6)    5cc. 

"     4-4  cc.    "    4-6  cc.  " 

Beginning  dehydration 

(7)  Sec. 

1     4-3  cc.    "    4-7  cc.  " 

Increasing  dehydration  with  sep- 

aration of  white  soap 

(8)   5cc. 

"     4-2  cc.    "    4-8  cc." 

Increasing  dehydration  with  sep- 

aration of  white  soap 

(9)  5cc. 

"     4-1  cc.    "    4-9  cc.  " 

Increasing  dehydration  with  sep- 

aration of  white  soap 

(10)   5cc. 

"     4-lOcc.  mKCiHiOj 

Increasing  dehydration  with  sep- 

aration of  white  soap 

(11)   See. 

"              "      4-  10  cc.  HiO  (control) 

Mobile  liquid 

TABLE   XXXIX 

POTASSIUM  OLEATE — Dipotassium  Sulphate 


Concentration  of  mixture. 

Remarks. 

(1)  See. 

potassium  oleate4-9  cc.  H»O4-1  cc.  m/2  KiSC>4 

Mobile  liquid 

(2)   5cc. 

"     4-8  cc.    "    4-2  cc.    " 

Mobile  liquid 

(3)   5cc. 

"     4-7  cc.    "    4-3  cc.    " 

Liquid 

(4)   5cc. 

"     4-6  cc.    "    4-4  cc.    " 

Liquid 

(5)    5cc. 

"     4-5  cc.    "    4-5  cc.     "        " 

Increasing  viscidity 

(6)   5  cc. 

"     4-4  cc.    "    4-6  cc.     " 

Increasing  viscidity 

(7)   Sec. 

"     4-3  cc.    "    4-7  cc.    " 

Increasing  viscidity 

(8)   5cc. 

"     4-2  cc.    "    4-8  cc.    " 

Increasing  viscidity 

(9)   Sec. 

"     4-1  cc.    "    4-9  cc.    " 

Gel 

(10)    5cc. 

"     4-lOcc.  m/2KzSO4 

Gel 

(11)   5cc. 

"     4-  10  cc.  HjO  (control) 

Mobile  liquid 

126 


SOAPS  AND  PROTEINS 


TABLE  XL 
POTASSIUM  OLEATE — Dipotassium  Tartrate 


Concentration  of  mixture. 

Remarks. 

(1)  5cc. 

potassium  oleate+9  cc.  HiO  +  1  cc.  mKiC^Oe 

Mobile  liquid 

(2)   5cc. 

"     +8  cc.    "    +2  cc.  " 

Liquid 

(3)   5cc. 

"     +7  cc.    "    +3  cc.  " 

Viscid  liquid 

(4)   5  cc. 

"     -|-6  cc.    "    +4  cc.  " 

Gel 

(5)   5cc. 

"     +5  cc.     "    +5  cc.  " 

Stiffest  gel 

(6)   5cc. 

"     +4  cc.     "    +6  cc.  " 

Gel 

(7)   5cc. 

"     +  3  cc.    "    +7  cc.  " 

Gel 

(8)   5cc. 

"     +2  cc.    "    +8cc.  " 

Viscid  liquid 

(9)   5  cc. 

"     -f-1  cc.    "    +9  cc.  " 

Liquid 

(10)   5cc. 

"     +  10cc.  mKiC<H4O6 

Liquid 

(11)   5cc. 

"     +10  cc.  HjO  (control) 

Mobile  liquid 

TABLE   XLI 

POTASSIUM  OLEATE — Dipotassium  Phosphate 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium  oleate+9  cc.  HiO  +  1  cc.  m  KiHPO4 


(2)  5cc. 

(3)  5cc. 

(4)  5cc. 

(5)  5cc. 

(6)  5cc. 

(7)  See. 

(8)  5cc. 

(9)  5cc. 

(10)  See. 

(11)  5cc. 


+8  cc.  ' 

+  7  cc.  ' 

+  6cc.  " 

+  5oc.  " 

+4cc.  " 

+3cc.  " 

+2  cc.  " 

-f-lcc.  " 

+  10  cc.  m 


"     +10  cc.  HiO  (control) 


4-2  cc. 
+  3  cc. 
+4cc. 
+5  cc. 
+6cc. 
+  7  cc. 
4-8  cc. 
+9cc. 


Mobile  liquid 

Liquid 

Clear  viscid  liquid 

Clear  stiff  gel    • 

Turbid  liquid 

Turbid  liquid 

Turbid  liquid 

Beginning  dehydration 

Greater  dehydration 

Greatest  dehydration,  dispersion 

medium  milky 
Mobile  liquid 


TABLE   XLII 

POTASSIUM  OLEATE — Tripotassium  Citrate 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  poti 

isium  oleate   +9  cc.  HtO  +  1  cc.  m    KiC»HiC>7 

Mobile  liquid 

(2)   5cc. 

"     +8cc.     "    +2cc.  " 

Liquid 

(3)   See. 

"     +7cc.     "    +3cc.  " 

Clear  gel 

(4)   5cc. 

"     +  6cc.     "    +4  cc.  " 

Clear  viscid  liquid 

(5)   5cc. 

"     +  5cc.     "    +5cc.  " 

Clear  liquid 

(6)   Sec. 

"     +4  cc.     "    +6cc.  " 

Turbid  liquid 

(7)   See. 

"     +3  cc.     "    +7cc.  " 

Beginning  dehydration 

(8)   5  cc. 

"     +2cc.     "    +8cc.  " 

Great  dehydration 

(9)   5cc. 

"      +1  cc.     "    +9cc.  " 

Great  dehydration 

(10)   5cc. 

"     +10cc.  mKjC.HtOT 

Great  dehydration 

(11)  5cc. 

"     +10cc.  HiO 

Mobile  liquid 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


127 


TABLE   XLIII 
POTASSIUM  OLE  ATE — Potassium  Hydroxid+ Potassium  Chlorid 


Concentration  of  mixture. 

Remarks. 

(1)   5  cc. 

potassium  oleate  -f  2cc.5nKOH4-7cc.  HzO-f  Ice.  m  KC1 

Stiff  gel 

(2)  5cc. 

"     4-2  cc.  "       "     +6cc.    "    +2cc.  "     " 

Stiff  gel 

(3)   5cc. 

"     +2cc    "       "     4-5  cc.    "    4-3cc.  "     " 

Stiff  gel 

(4)   5cc. 

"     -f2cc.  "       "     +4  cc.    "    +4  cc."     " 

Stiff  gel 

(5)   5cc. 

"     4-2cc.  "       "     4-3cc.    "    4-5cc.  "     " 

Less    stiff    gel,    slightly 

turbid 

(6)   5cc. 

"      4-2  cc.  "       "     4-2  cc.    "    4-6  cc."     " 

Decreasingly    stiff    gel. 

slightly  turbid 

(7)  5cc. 

"      4-2  cc.  "       "     4-lcc.    "    4-7cc.  "     " 

Decreasingly    stiff    gel, 

slightly  turbid 

(8)   5cc. 

"     4-2  cc.  "       "     4-8  cc.  mKCl 

Decroasingly    stiff    gel, 

slightly  turbid 

(9)   5cc. 

"     4-2  cc.  "       "     4-8  cc.  H2<D  (control) 

Gel 

(10)  5cc. 

"      4-10  cc.  HiO  (control) 

Mobile  liquid 

TABLE   XLIV 

POTASSIUM  OLEATE — Potassium  Hydroxid+ Potassium  Chlorid 


Concentration  of  mixture. 

Remarks. 

(1)  5cc. 

potassium  oleate  4-2  cc. 

10nKOH4-7cc. 

H2O  +  lcc.  mKCl 

Gel,    beginning    dehy\ 

dration 

(2)   5cc. 

"      4-2  cc. 

"     4-6  cc. 

"    +2  cc.  "    " 

Gel,    increasing    dehy- 

dration 

(3)   5cc. 

"      4-2  cc. 

"     4-5  cc. 

"    +3  cc.  "    " 

Gel,    increasing    dehy- 

dration 

(4)   5cc. 

"      4-2cc. 

"        "     +4cc. 

"    4-4cc.  "    " 

Gel,    increasing    dehy- 

dration 

(5)  5cc. 

"      4-2cc. 

"     4-3  cc. 

"    4-5  cc.   "    " 

Gel,    increasing    dehy- 

dration 

(6)   5cc. 

"      4-2  cc. 

"     +2  cc. 

"    +6cc.  "    " 

Gel,    increasing    dehy- 

dration 

(7)   5cc. 

"      4-2cc. 

"     4-lcc. 

"    4-7  cc.  "    " 

Gel,    increasing    dehy- 

dration 

(8)   5cc. 

"      4-2cc. 

"     4-8  cc. 

m  KC1 

Marked      dehydration 

and  separation 

(9)   5cc. 

"      4-2cc. 

"     +8cc. 

HzO  (control) 

Clear  gel 

(10)   5cc. 

"      4-10  cc.  HiO  (control) 

Mobile  liquid 

128 


SOAPS  AND  PROTEINS 


TABLE   XLV 
POTASSIUM  OLE  ATE — Potassium  Chlorid+ Potassium  Hydroxid 


Concentration 

of  mixture. 

Remarks. 

(1)  5cc. 

potassium  oleate-f  2  cc.  mKCl  +  7  cc.  HjO  +  1  cc.  5  n  KOH 

Viscid 

(2)   5cc. 

"     +2cc.  " 

"    +6  cc.     ' 

+  2cc.   " 

Stiff  gel 

(3)    5cc. 

"     +2  cc.  " 

"    +5  cc.    ' 

+  3  cc.   " 

Stiff  gel 

(4)    5cc. 

"     +2  cc.  " 

"    -f-4cc.     " 

+4cc.   " 

Less   stiff  gel,   begin- 

ning dehydration 

(5)    5cc. 

"     +2cc.  ' 

"    +3cc.     " 

+  5cc.   " 

Increasing     dehydra- 

tion and  separation 

(6)   See. 

*•      +2cc.  ' 

"    +2  cc.     " 

+6cc.   " 

Increasing     dehydra- 

tion and  separation 

(7)   5cc. 

"              "     -|-2  cc.  ' 

"    -j-1  cc.     " 

+  7  cc.   " 

Increasing     dehydra- 

tion and  separation 

(8)    5  cc. 

"     +2  cc.  ' 

"    +8  cc.  5  n 

KOH 

Increasing     dehydra- 

tion and  separation 

(9)   5cc. 

'•      +2  re.  ' 

'     "    +8  cc.  HzO  (control) 

Mobile  liquid 

(10)    5  cc. 

"      +  10cc. 

HiO  (control) 

Mobile  liquid 

TABLE   XLVI 

POTASSIUM  OLE  ATE — Potassium  Hydroxid + Sodium  Chlorid 


Concentration  of  mixture. 

Remarks. 

(1)  5cc.  potassium  oleate  +  2  cc.  5  n  KOH  +7  cc.  HiO  +  1  cc.mNaCl 

Stiff  gel 

(2)   5cc. 

1      -1-2  cc.  ' 

+  6cc. 

*    +2cc.  " 

Stiff    gel,    slight    tur- 

bidity 

(3)   See. 

"     +2cc.  ' 

'       "      +  5ec. 

"    +  3cc.  "     " 

Stiff    gel,    slight    tur- 

bidity 

(4)   5cc. 

"      -|-2cc.  ' 

"      -f4cc. 

"    +4cc.  "     " 

Stiff    gel,    slight    tur- 

bidity 

(5)    See. 

**     +2  cc.  ' 

"      +3cc. 

"    +5CC.  "     " 

Stiff,    gel    slight    tur- 

bidity 

(6)   5cc. 

"     +2  cc.' 

"      +2cc. 

"    +6cc.  "    " 

Gel     with     beginning 

dehydration     and 

separation 

(7)   5cc. 

"     +2cc.  ' 

'       "      -J-lcc. 

"    -|-7cc.  "     " 

Great        dehydration 

and  separation 

(8)   5cc. 

4  '     +2  cc.  ' 

"      -|-8  cc. 

m  NaCl 

Great        dehydration 

and  separation 

(9)   See. 

"     +2cc.  ' 

"      +8cc. 

HzO  (control) 

Viscid 

(10)   5cc. 

"     -f-10cc. 

HiO  (control) 

Mobile  liquid 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


129 


TABLE    XLVII 

POTASSIUM  OLE  ATE — Sodium  CMorid-}- Potassium  Hydroxid 


Concentration  of  mixture. 

Remarks. 

(1)  5cc. 

potassium  oleate  +  2  cc.  m  NaCl  +7  cc.  HiO  +  1  cc.  5  n  KOH|  Viscid 

(2)   5cc. 

"     +2cc.  ' 

'     +6cc.     "    +2  cc.    " 

Stiff  gel 

(3)   5cc. 

"     +2cc.  ' 

'      "     +5  cc.     "    +3cc.   "    " 

Stiff    gel,   slight   tur- 

bidity 

(4)   5cc. 

"     -f-2cc.  ' 

'      "     +4cc.     "    +4cc.    "    " 

Stiff     gel,     beginning 

dehydration        and 

separation 

(5)   5cc. 

"      +2cc.  ' 

'      "     -f-3  cc.     "    +5  cc.    "     ' 

Increasing     dehydra- 

tion and  separation 

(6)   5cc. 

"      +2cc.  ' 

'      "     +  2cc.     "    +  6cc.    "     " 

Increasing     dehydra- 

tion and  separation 

(7)   5cc. 

"      +2cc.  ' 

'      "     +lcc.     "    +  7cc.   "    " 

Increasing     dehydra- 

tion and  separation 

(8)   occ. 

"     +2cc.  ' 

'      "     +8cc.  5nKOH 

Increasing     dehydra- 

tion and  separation 

(9)  5cc. 

"     +2cc.  ' 

'     "     +8  cc.  HjO  (control) 

Mobile  liquid 

(10)   5cc. 

"     -1-lOcc. 

HjO  (control) 

Mobile  liquid 

TABLE   XLVIII 

POTASSIUM  OLEATE — Potassium  Chlorid 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium  oleate+9  cc.  HiO  +  1  cc.  m  KC1 

Liquid 

(2)  5cc. 

'      +8cc.     "    +2cc.  " 

Liquid 

(3)   5  cc. 

"     +7  cc.     "    +3  cc.  "     " 

Liquid 

(4)   5  cc. 

"     +6  cc.     "    -|-4  cc.  "     " 

Slightly  viscid 

(5)   5cc. 

"     +  5cc.     "    +5  cc.  "     " 

More  viscid 

(6)   5cc. 

"     +4  cc.     "    +6cc.  "     " 

Gel 

(7)  5cc. 

"     +3cc.     "    +7  cc.  "     " 

Gel 

(8)  5cc. 

"     +2cc.     "    +8cc.  "     " 

Stiff  gel 

(9)  See. 

"     +1  cc.     "    +9cc.  "     " 

Stiff  gel 

(10)   5cc. 

"     -flOcc.  m  KC1 

Stiff  gel 

(11)   See. 

"      +10  cc.  HjO  (control) 

Mobile  liquid 

130 


SOAPS  AND  PROTEINS 


TABLE   XLIX 

POTASSIUM  OLEATE — Sodium  Chlorid 


Concentration  of  mixture. 

Remarks. 

(1)  5cc. 

potassium  oleate  +  9  cc. 

HjO  +  1  cc.  m  NaCl 

Liquid 

(2)   5cc. 

"     -fScc. 

"    +2cc.  "      " 

Liquid 

(3)   See. 

"     +  7cc. 

"    +3cc.  "      " 

Slightly  viscid 

(4)   5cc. 

"     +6cc. 

"    +4cc.  "      " 

Gel 

(5)   5cc. 

"     +5cc. 

"    +5cc.  •'      " 

Gel 

(6)   5cc. 

"     -|-4cc. 

"    +6cc.  "      " 

Gel 

(7)   5  cc. 

"     +3  cc. 

"    +7cc.  "      " 

Less  viscid  gel 

(8)   5cc. 

"     +2cc. 

"    +8cc.  "      " 

Beginning  dehydration  and  sepa- 

ration 

(9)   5cc. 

"     +  lcc. 

"    +9cc.  "      " 

Increased  dehydration 

and  sepa- 

ration 

(10)   5cc. 

"      +10  cc 

m  NaCl 

Increased  dehydration 

and  sepa- 

ration 

(11)   5cc. 

"     +10  cc 

HjO  (control) 

Mobile  liquid 

TABLE   L 
POTASSIUM  OLEATE — Ammonium  Chlorid 


Concentration  of  mixture. 

Remarks. 

(1)   5cc. 

potassium  oleate-f  9  cc. 

H»O  +  lcc.  mNH4Cl 

Mobile,  slightly  turbid  liquid 

(2)  See. 

"     +8cc. 

"    +2cc.  " 

Mobile,  slightly  turbid  liquid 

(3)   See. 

"     +7cc. 

"    +3  cc.  " 

Mobile,  slightly  turbid  liquid 

(4)   See. 

"     +6  cc. 

"    -f4cc.  " 

Mobile.slightly  turbid  liquid  with 

progressively  thicker  collar 

(5)  5cc. 

"     +5cc. 

"    +5  cc.  " 

Mobile,  slightly  turbid  liquid  with 

progressively  thicker  collar 

(6)  See. 

"     +4cc. 

"    +6cc.  " 

Mobile,  slightly  turbid  liquid  with 

progressively  thicker  collar 

(7)   5cc. 

"     +3cc. 

"    +7cc.  " 

Mobile,  slightly  turbid  liquid  with 

progressively  thicker  collar 

(8)  5cc. 

"     +2cc. 

"    +8  cc.  " 

Mobile,  slightly  turbid  liquid  with 

progressively  thicker  collar 

(9)  5cc. 

"     +lcc. 

"    4-9  cc.  " 

White  mobile  liquid 

(10)  5cc. 

'  '     +  10  cc 

m  NH4C1 

White  mobile  liquid 

(11)  Sec. 

"      +  10ec 

H*O  fcontrol) 

Mobile  liquid 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


131 


TABLE   LI 
POTASSIUM  OLEATE — Magnesium  Chlorid 


Concentration  of  mixture. 


Remarks. 


(1)   5cc. 

potassium  oleat( 

•+  9cc. 

HiO  -f  1  cc.  m/100  MgCU 

Mobile  transparent  liquid 

(2)   5cc. 

,. 

+  8  cc. 

"    +2  cc. 

Slightly  cloudy 

(3)   5cc. 

,. 

+  5cc. 

"    +5cc.       " 

Mobile  milky  liquid 

(4)   5cc. 

.. 

+  10  cc. 

m/100  MgCh 

Mobile  milky  liquid 

(5)    5  cc. 

.  .              «  « 

+  8cc. 

HzO  +  2  cc.  m/10  MgCU 

Mobile  milky  liquid 

(6)   5cc. 

•  <              i  > 

+   5cc. 

"    +  5cc.      " 

Thick  milky  liquid 

(7)   5cc. 

..              .. 

+  10  cc. 

m/10  MgClz 

Thick  milky  liquid 

(8)   5cc. 

-(-lOcc. 

HiO  (control) 

Mobile  liquid 

TABLE   LII 

POTASSIUM  OLEATE — Calcium  Chlorid 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium  oleate  +  9  cc.  HzO  +  1  cc.  m/100  CaCh 

(2)  5cc.          "  "     +  8cc.     "    +2cc.       " 

(3)  5cc.          "  "     +   5cc.     "    +5cc. 


(4)  5cc. 

(5)  5cc. 

(6)  5cc. 

(7)  5cc. 

(8)  5  cc. 


+  10cc.  m/lOOCaCU 

+  8  cc.  HiO+2  cc.  m/10  CaCh 

+  5  cc.  "  +5  cc. 
+  10cc.  m/lOCaCk 
+  10cc.  H2O  (control) 


More  liquid  than  control 
Some  white  precipitate 
Increasing    amount    of    white 

precipitate 
Increasing    amount    of    white 

precipitate 
Increasing    amount    of    white 

precipitate 
Milky  white 
Fluid  as  water 
Mobile  liquid 


132 


SOAPS  AND  PROTEINS 


TABLE   LIII 
POTASSIUM  OLEATE — Cupric  Chlorid 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium  oleate  +  9.99  cc.  HsO+0.01  cc.  mCuCli 

(2)  5cc.          "  "     +9.8    cc.     "    +0.2    cc.  "     " 

(3)  5  cc.          "  "     -1-9.5    cc.     "    +0.5   cc.  "     " 

(4)  Sec.          "  "     +9.0    cc.     "    +1.0   cc.  "     " 

(5)  5cc.          "  "     +8.0    cc.     "    +2.0   cc.  "     " 


(6)  5cc. 

(7)  5cc. 

(8)  5cc. 

(9)  5cc. 

(10)  5cc. 

(11)  5cc. 

(12)  5cc. 

(13)  5cc. 

(14)  5cc. 


'  +7.0    cc.     "    +3.0  cc. 

"  +6.0    cc.     "    +4.0  cc. 

"  +5.0    cc.     "    +5.0  cc. 

"  +4.0    cc.     "    +6.0  cc. 

"  +3.0    cc.     "    +7.0  cc. 

"  +2.0    cc.     "    +8.0  cc. 

"  +1.0    cc.     "    +9.0  cc. 

4 '  + 10  cc.  m  CuCh 

"  +10  cc.  HiO  (control) 


Clear  liquid 

Turbid  liquid 

More  turbid  liquid 

Milky  liquid 

Dry    masses    of    copper    soap 

swimming  in  free  dispersion 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispersion 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispersion 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispeision 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispeision 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispersion 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispeision 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispeision 

medium 
Dry    masses    of    copper    soap 

swimming  in  free  dispersion 

medium 
Mobile  liquid 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


133 


TABLE  LIV 
POTASSIUM  OLEATE — Ferric  Chlorid 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  potassium  oleate  +  9  cc.  H2O  +  1  cc.  m/lOOFeCh 

(2)  5cc.  "  "      +  8cc.     "    +2cc.       " 


(3)  5cc.  +5cc.  "  +5cc. 

(4)  5cc.  "  "  +9cc.  "  +1  cc.  m/lOFeCU 

(5)  5cc.  "  "  +8  cc.  "  +2  cc.      " 

(6)  5cc.  "  "  +5cc.  "  +5cc.      " 

(7)  5cc.  "  "  +9cc.  "  +lcc.     m     Fed; 

(8)  5cc.  "  "  +8cc.  "  +2  cc. 

(9)  5cc.  "  "  +7cc  "  +3co. 

(10)  5cc.  "  "  +2cc.  "  +8cc. 

(11)  5cc.  "  + 10  cc.  H2O  (control) 


Turbid   liquid. 

Increasingly  turbid  liquid,  sus- 
pended particles  of  increasing 
size 

Increasingly  turbid  liquid,  sus- 
pended particles  of  increasing 
size 

Increasingly  turbid  liquid,  sus- 
pended particles  of  increasing 
size 

Increasingly  turbid  liquid,  sus- 
pended particles  of  increasing 
size 

Increasingly  turbid  liquid,  sus- 
pended particles  of  increasing 
size 

Reddish  coagulum  of  iron  soap 
floating  in  freed  dispersion 
medium 

Reddish  coagulum  of  iron  soap 
floating  in  freed  dispersion 
medium 

Reddish  coagulum  of  iron  soap 
floating  in  freed  dispersion 
medium 

Reddish  coagulum  of  iron  soap 
floating  in  freed  dispersion 
medium 

Mobile  liquid 


134 


SOAPS  AND  PROTEINS 


TABLE 

GELATION  AND  SALTING-OUT  OF  VARIOUS  FATTY 


Amount 

Condition  of  mixtures  after  24  hours  upon  addition 

Mol  wt. 

Fatty  acid. 

acid  used 

in  grams 

(VM  mol). 

n 

2n 

3n 

4  n 

5n 

46 

Formic 

0.0727 

Clear  liquid 

Clear  liquid 

Clear  liquid 

Clear  liquid 

Clear  liquid 

60 
74 

Acetic 
Propionic 

0.0948 
0.1169 

88 
102 

Butyric 
Valeric 

0.1390 
0.1612 

116 
144 

Caproic 
Caprylic 

0.1832 
0.2275 

Solid  white 

Solid  white 

soap 

soap 

172 

Capric 

0.2718 

.. 

Solid  white 

Solid  white 

Partly 

Completely 

soap 

soap 

salted  out 

salted  out 

200 

Laurie 

0.3160 

Solid  white 

Solid  white 

Solid  white 

Completely 

Completely 

soap 

soap 

soap 

salted  out 

salted  out 

Tube  n  u  i 

nber 

1 

2 

3 

• 

5 

THE  COLLOID-CHEMISTRY  OF  SOAPS 


135 


LV 

ACID — ALKALI  MIXTURES  OF  THE  ACETIC  SERIES 


at  20°  C.  of  5  cc.  sodium  hydroxid  of  the  following  concentrations: 


6n 

7n 

8n 

9n 

10  n 

11  n 

12  n 

H,O 

Clear  liquid 

Clear  liquid 

Clear  liquid 

Clear  liquid 

Clear  liquid 

Clear  liquid 

Clear  liquid 

Clear  liquid 

44 

Completely 
salted  out 

Completely 
salted  out 

4.                     .4 

ing  out 

»v 

44                       4. 

.. 

Viscid  white 
soap 

Slight  salt- 
ing out 

Completely 
salted  out 

Completely 
salted  out 

4, 

,. 

Viscid  white 
soap 

Partly 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

.4 

Viscid  white 
soap 

Viscid  white 
soap 

Viscid  white 
soap 

Solid  white 
soap 

Solid  white 
soap 

Solid  white 
soap 

Completely 
salted  out 

Acid  float- 
ing on 
water 

Solid  white 
soap 

Solid  white 
soap 

Partly 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Acid  float- 
ing on 
water 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Acid  float- 
ing on 
water 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Completely 
salted  out 

Acid  float- 
ing on 
water 

6 

7 

8 

9 

10 

11 

12 

Control 

136  SOAPS  AND  PROTEINS 


XI 

THE  FOAMING,  EMULSIFYING  AND  WASHING  PROPERTIES 

OF   SOAPS 

There  is  still  much  debate  as  to  what  is  the  property  of  soaps 
(and  similarly  acting  compounds)  which  when  added  to  water 
favors  the  production  and  maintenance  of  foams  or  emulsions. 
Without  first  entering  upon  a  discussion  of  the  theories  which 
have  been  proposed,  what  do  the  colloid-chemical  facts  outlined 
in  the  preceding  pages  contribute  toward  a  possible  solution 
of  the  problem?  In  the  several  series  of  soaps  described  we  have 
thus  far  correlated  their  chemical  composition  and  that  of  the 
various  "  solvents "  used  with  them,  with  various  physico- 
chemical  properties  of  the  resulting  systems.  What  is  the  relation- 
ship between  such  a  property  of  a  soap  as  its  hydration  capacity 
and  its  ability  to  yield  a  foam;  or  what  is  the  relationship  between 
this  hydration  value  and  the  production  and  maintenance  of  an 
emulsion?  A  proper  answer  to  these  questions  may  prove  of 
help  for  the  solution  of  that  secondary  technological  problem 
which  concerns  the  washing  properties  of  soap,  which,  as  now 
held  by  various  authors,  are  intimately  associated  with  its  foaming 
and  emulsifying  qualities.  The  following  paragraphs  show  that 
the  foaming,  emulsifying  and  washing  properties  of  soaps  are  a 
function,  in  the  main,  of  their  hydrophilic  colloid  character.  Only 
those  soaps  foam  or  emulsify  which  under  the  conditions  of  their  use 
yield  liquid  and  hydrated  colloids. 

1.  The  Foaming  Properties  of  Soaps 

We  need  to  begin  these  paragraphs  by  a  definition  of  what 
constitutes  a  foam.  As  ordinarily  understood,  it  is  a  subdivision 
of  a  gas  in  a  liquid.  There  exist  also,  however,  what  may  be 
termed  solid  foams,  namely,  subdivisions  of  a  gas  in  a  solid,  as 
in  ordinary  pumice,  but  since  such  solid  foams  were  invariably 
produced  when  the  now  solid  phase  was  liquid,  these  are  really 
only  a  subclass  of  the  liquid  foams.  When  not  otherwise  specified 
we  refer  in  these  pages  only  to  the  liquid  foams  and  the  conditions 
surrounding  their  production  and  maintenance. 


THE  COLLOID-CHEMISTRY  OF  SOAPS  137 

It  is  of  importance  next  to  distinguish  between  the  production 
of  a  foam  and  its  maintenance  after  production.  Authors  who 
have  written  on  this  subject  have  rarely  done  so.  Mere  contact 
between  a  gas  and  a  foaming  agent  does  not  produce  a  foam — the 
gas  must  be  stirred,  blown  or  mixed  into  it.  When  we  speak 
off-hand  of  a  foam-producing  material  we  really  mean  something 
which  will  stabilize  the  foam  once  it  is  produced. 

51 

In  order  to  discover  if  any  relationship  existed  between  the 
colloid  properties  (or  more  particularly  the  hydration  capacities) 
of  different  soaps  and  their  foaming  qualities  we  chose  for  first 
study  the  sodium  soaps  of  the  acetic  acid  series.  To  obtain  com- 
parable results,  10  cc.  of  equimolar  "  solutions  "  of  the  different 
soaps  were  placed  in  tall  test-tubes  (30  cm.X2  cm.)  and  shaken. 
In  order  that  all  might  be  treated  equally  from  the  point  of  view 
of  foam  production,  all  the  tubes  were  clamped  in  a  frame,  the 
shaking  being  continued  for  thirty  seconds.  For  reasons  which 
will  become  clear  later,  the  temperature  is  an  important  factor 
and  must  be  watched  carefully.  Moreover,  since  the  systems 
resulting  at  any  fixed  temperature  when  soap/water  mixtures 
are  brought  to  the  desired  temperature  from  a  higher  point  differ 1 
from  those  which  result  when  they  are  brought  to  such  temper- 
ature from  a  lower  one,  all  the  soap  "  solutions  "  about  to  be 
described  were  started  at  a  low  temperature  and  then  brought 
to  the  higher  ones.  Tubes,  water  and  soaps  were  therefore  all 
first  reduced  to  the  lowest  temperature  used  in  these  experiments, 
namely,  8°  C.  After  they  had  remained  at  this  temperature  for 
twenty-four  hours  the  proper  molar  solutions  were  made  by  mix- 
ing the  soaps  with  the  water.  After  another  period  (twenty- 
four  hours)  of  standing  and  careful  mixture  until  (apparent) 
homogeneity  had  been  attained,  the  tubes  were  shaken  violently 
for  thirty  seconds  to  permit  of  the  formation  of  foam.  They 
were  photographed  after  four  minutes,  then  left  to  themselves 
for  two  hours,  still  in  the  thermostat,  and  photographed  a  second 
time.  After  this  first  series  of  observations,  the  tubes  with  their 
reaction  mixtures  were  then  warmed  to  the  next  higher  temper- 
ature, namely,  26°  C.  and  kept  at  this  for  twenty-four  hours. 

1  See  page  74. 


138  SOAPS  AND  PROTEINS 

After  shaking,  photographing,  allowing  to  rest  and  rephoto- 
graphing,  we  repeated  the  whole  process  at  50°  C.  and  finally 
at  100°  C. 

The  results  obtained  in  the  case  of  the  sodium  soaps  of  the 
acetic  acid  series  at  the  concentration  2  m.  are  shown  in  the  photo- 
graphs of  Figs.  77  and  78.  This  was  really  an  attempt  to  dis- 
cover where  in  the  series  and  at  what  concentration  foaming 
will  begin.  At  8°  C.  (the  lowermost  row  of  tubes  in  Fig.  77) 
it  is  apparent  that  no  foam  is  formed  by  the  formate,  acetate, 
propionate,  butyrate  or  valerate  of  sodium.  There  is  just  a  sug- 
gestion of  a  foam  in  the  case  of  the  caproate,  but  clear  formation 
of  such  does  not  begin  until  the  caprylate  is  reached.  At  this 
temperature  soaps  higher  l  in  the  series  fail  to  yield  homogeneous 
mixtures  ("  solutions  ")  with  the  water.  The  mixtures  also  do 
not  foam.  The  absence  of  the  tubes  from  the  series  in  this 
and  the  subsequent  photographs  expresses  this  fact. 

When  the  temperature  is  raised  to  26°  C.  the  findings  are  much 
the  same  except  that  the  caproate  shows  no  signs  of  foaming  and 
the  caprylate  less  than  at  the  lower  temperature.  At  50°  and 
100°  C.  the  picture  is  largely  repeated — the  caprylate  alone  foams, 
though  less  than  at  the  lower  temperatures.  Fig.  78,  which 

1  These  higher  soaps  take  up  the  water  offered  them  but  yield  such  viscid 
systems  that  they  are  practically  solid.  In  consequence,  air  cannot  be  easily 
shaken  or  beaten  into  them.  Just  as  in  the  case  of  the  emulsions  (see  MARTIN 
H.  FISCHER  and  MARIAN  O.  HOOKER:  Fats  and  Fatty  Degeneration,  36, 
New  York  (1917))  the  production  of  a  foam  is  best  accomplished  when  the  soap 
is  present  in  a  medium  concentration  and  when  the  resulting  system  is  essen- 
tially a  liquid  hydra  ted  colloid.  At  ordinary  temperatures  the  soaps  of  the 
acetic  series,  especially  the  higher  ones,  are  all  more  solid  even  in  the 
presence  of  considerable  water,  than  the  soaps  of  the  less  saturated  fatty 
acids.  For  this  reason  none  of  them  is  as  good  a  foaming  or  emulsifying 
agent  as  an  oleate,  linolate  or  other  liquid  soap. 

In  general,  the  melting  points  of  the  soaps  of  the  acetic  series  lie  par- 
allel to  but  above  that  of  their  fatty  acids.  All  the  fatty  acids  below 
caproic  are  liquid  near  0°  C.  or  below.  Caprylic  acid  is  liquid  at  16.5°; 
capric  at  31.3°;  lauric  at  43.6°;  myristic  at  53.8°;  palmitic  at  62°;  margaric 
at  60°;  stearic  at  69.3°;  arachidic  at  77°  C. 

The  lowermost  soaps  of  the  acetic  series  are  "soluble"  in  water  and  yield 
liquid  systems  even  at  a  low  temperature.  In  the  middle  of  the  series  and  at 
ordinary  temperatures  the  acetic  series  soaps  yield  liquid  hydrated  colloid 
systems  with  water,  and  are  the  best  foam  producers.  Above  this  they  yield 
highly  viscid  to  solid  hydrated  systems  and  less  favorable  ones  for  foam  pro- 
duction. Rise  in  temperature  shifts  the  whole  arrangement  to  the  right,  the 
lower  soaps  going  into  the  region  of  the  true  solutions  of  soap  in  water  and 
thus  losing  their  foaming  qualities  while  the  higher  ones  move  from  the  region 
of  the  hydrated  solid  colloids  into  that  of  the  hydrated  liquid  ones. 


THE  COLLOID-CHEMISTRY  OF  SOA^S 


FIGURE  77. 


FIGURE  78. 


140  SOAPS  AND  PROTEINS 

shows  the  appearance  of  these  tubes  two  hours  later,  indicates 
that  the  foams  do  not  last.  They  die  down  fastest  at  the  higher 
temperatures,  the  greatest  permanency,  in  other  words,  being 
shown  by  the  foams  produced  at  the  lower  temperatures. 

It  is  well  to  state  at  once  what  we  hold  to  be  the  relationship 
between  these  findings  and  our  previous  considerations  of  the 
hydrophilic  properties  of  these  soaps.  The  lowermost  soaps  form 
only  solutions  in  water,  they  show  no  hydrophilic  properties, 
and  they  do  not  foam.  Sodium  caprylate,  with  its  more  distinct, 
even  though  still  low,  hydration  capacity,  yields  the  first  satis- 
factory foam.  It  does  this  best,  however,  at  a  low  temperature. 
At  this  it  has  its  highest  hydrophilic  value.  To  raise  the  temper- 
ature of  this  soap/water  system  is  to  make  the  sodium  caprylate 
go  into  true  solution  in  the  water,  and  as  this  happens  the  hydro- 
philic colloid  properties  of  the  system  are  diminished,  and,  simi- 
larly, the  foaming  properties.  The  higher  soaps  do  not  foam 
because  not  enough  of  them  "  goes  into  solution "  to  yield  a 
(liquid)  hydrated  colloid  system — the  water,  in  other  words, 
is  either  taken  up  to  form  an  essentially  solid  mixture  into  which 
the  air  cannot  be  driven,  or  the  soap  is  so  "  insoluble  "  that 
the  water  remains  "  free  "  and  hence  there  is  no  lasting  foam. 


§2 

It  will  be  noticed  that  the  first  foaming  qualities  in  these 
soaps  developed  in  the  experiment  just  described  at  the  concen- 
tration 2m.  If  the  experiment  with  these  soaps  is  repeated  at 
the  concentration  m,  the  previously  foaming  soaps  no  longer  foam 
while  soaps  higher  in  the  series  which  did  not  foam  now  do  so.  The 
former  of  these  truths  is  readily  apparent  if  the  vertical  set  of 
tubes  marked  7  (the  caprylate)  in  Fig.  77  is  compared  with  the 
similarly  numbered  set  of  Fig.  79.  To  explain  this  finding  we 
would  say  that  in  the  lower  concentration  of  sodium  caprylate 
illustrated  in  Fig.  79  the  soap  is  more  nearly  in  "  true  "  solution 
and  that  the  hydrophilic  properties  of  the  system  are  diminished 
in  proportion.  But  the  next  higher  soap,  namely,  sodium  caprate 
(the  tubes  8  of  Fig.  79)  foam  nicely.  At  8°  the  sodium  caprate 
does  not  foam.  Most  foaming  is  obtained  at  26°,  with  less  at 
the  two  higher  temperatures  50°  and  100°  C. 

To  explain  these  findings  it  must  be  recalled  that  at  the  tern- 


THE  COLLOID-CHEMISTRY  OF  SOAPS  141 

perature  8°  C.  sodium  caprate  is  still  solid  and  remains  essentially 
only  mechanically  subdivided  in  the  water.  When  the  temper- 
ature is  raised  to  26°  C.  the  " liquefaction"  point  of  the  soap  in 
water  is  exceeded.  In  this  region  most  of  the  soap  is  in  the 
state  of  a  (liquid)  hydrophilic  colloid,  least  in  true  solution,  and 
the  greatest  foam  production  is  in  consequence  manifest.  At 
the  two  higher  temperatures  a  shift  in  the  soap/water  system 
occurs  in  the  direction  of  true  solution  of  the  soap  in  the  water 
at  the  expense  of  the  water  in  the  soap  fraction  and  hence  the 
diminished  tendency  to  foam. 

Fig.  79  shows  well  how  this  general  law  is  repeated  as  we 
ascend  in  the  soap  series.  Sodium  laurate  fails  to  foam  at  the 
temperatures  8°  and  26°  C.  At  50°  a  decided  foam  appears 
as  evidenced  in  the  tubes  marked  9,  the  foaming  being  increased 
at  100°  C.  Sodium  myristate  fails  to  foam  at  the  three  lower 
temperatures.  At  100°  C.,  as  shown  in  the  tube  marked  10  of 
the  top  row  of  Fig.  79,  it  foams  beautifully.  Not  until  the  temper- 
ature lies  above  50°  does  the  myristate  yield  a  (liquid)  hydro- 
philic  colloid  (and  a  foam).  Even  at  this  highest  temperature 
sodium  palmitate,  as  indicated  in  tube  11  of  Fig.  79,  foams  only 
badly.  The  soap  absorbs  all  the  water  offered,  to  yield  a  thick, 
gelatinous  mass  into  which  the  air  does  not  enter  easily.  The 
resulting  foam  is  therefore  practically  a  solid  one. 

Fig.  80  shows  how  the  tubes  just  described  look  two  hours 
later.  It  is  easily  observed  that  the  foams  die  down  most  rapidly 
(a)  in  the  lower  soaps  and  (6)  at  the  higher  temperatures. 

§3 

Figs.  81  and  82  respectively  show  the  foaming  characteristics 
of  the  sodium  soaps  of  the  acetic  series  at  the  concentration  m/2 
immediately  after  the  production  of  the  foams  and  two  hours 
later.  It  will  be  observed  that  at  this  concentration  the  caprate 
is  the  lowest  member  to  yield  a  foam;  the  amount  of  foam 
produced  in  all  the  caprate  tubes  of  this  series  (the  vertical  row 
marked  8)  is  distinctly  less  than  in  the  corresponding  set  of  tubes 
of  Fig.  79.  The  laurate  foams  at  this  lower  concentration  almost 
as  well  as  at  the  higher  concentration  previously  described.  It 
is  noteworthy,  however,  that  in  Fig.  79  (the  concentration  m) 
the  better  foam  is  obtained  at  the  temperature  of  100°  C. ;  in  Fig. 


142  SOAPS  AND  PROTEINS 

81  (the  concentration  m/2)  at  50°  C.  This  is  dependent,  in  our 
judgment,  upon  the  more  perfect  solubility  at  the  lower  con- 
centration of  the  laurate  in  the  water,  with  diminution  of  its 
hydrophilic  colloid  properties  as  the  temperature  is  raised. 


FIGURE  79. 

Fig.  82  shows  the  appearance  of  the  foaming  soaps  just 
described  after  having  been  left  to  themselves  for  two  hours  at  the 
designated  temperatures  and  again  demonstrates  that  foams  die 
down  fastest  in  the  lower  soaps  and  at  the  higher  tempera- 
tures. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


143 


§4 

In  order  to  test  further  the  general  truth  of  the  relationship 
between  hydration  capacity  and  foaming  qualities  of  the  different 
soaps,  we  next  studied  the  potassium  soaps  of  the  acetic  acid 
series.  As  previously  described,1  the  potassium  soaps  are  more 
soluble  in  water  and  have  a  higher  solubility  for  water  than  the 
corresponding  sodium  soaps.  It  was  in  consequence  to  be  expected 
at  a  given  concentration  (a)  that  the  potassium  soaps  would  not 
begin  foaming  as  early  as  the  corresponding  sodium  soaps,  (b)  that 
this  foaming  quality  would  be  lost  earlier  with  increase  in  temper- 


FIGURE  80. 

ature  and  (c)  that  the  soaps  of  the  higher  fatty  acids  would  show 
distinct  foaming  qualities  at  temperatures  at  which  the  corresponding 
sodium  soaps  would  be  so  "  insoluble  "  or  yield  such  solid  systems 
with  water  as  to  make  foaming  impossible.  The  truth  of  these 
1  See  pages  14  and  23. 


144 


SOAPS  AND  PROTEINS 


general   statements    is    illustrated  in  Figs.   83,   84,   85,    86,   87 
and  88. 

Fig.  83  shows,  when  compared  with  Fig.  77,  that  the  foaming 
of  2  m  potassium  soaps  at  four  different  temperatures  does  not 
begin  until  potassium  caprylate  is  reached.  This  soap  foams 
slightly  at  8°  C.  but  loses  this  quality  as  soon  as  the  temperature 
is  increased.  The  first  potassium  soap  to  show  a  lasting  foam 
at  the  several  temperatures  is  the  caprate  (the  tubes  8  of  Fig. 


FIGURE  81. 

83).  Fig.  84  shows  the  appearance  of  these  tubes  two  hours 
later.  The  foam  has  disappeared  entirely  from  the  only  caprylate 
which  showed  foaming  qualities  and  from  the  caprate  kept  at 
the  highest  temperature. 

Figs.  85  and  86  show  the  behavior  of  potassium  soaps  of  the 
acetic  series  at  the  concentration  m.  The  caprate  is  the  first 
in  the  series  to  foam,  but  the  laurate  and  myristate  also  foam. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


145 


The  potassium  soaps,  it  is  obvious,  begin  to  foam  at  lower  temper- 
atures than  the  corresponding  sodium  soaps  (see  Fig.  79)  but 
they  also  lose  this  quality  sooner  with  increase  in  temperature. 
When  the  tube  marked  11  of  the  potassium  series  (Fig.  85)  is 
compared  with  the  corresponding  tube  of  the  sodium  series 


FIGURE  82. 

(Fig.  79)  the  more  liquid  character  of  the  potassium  soap/water 
system  evidences  itself  by  the  better  foam  production.  Fig. 
86  shows  how  the  foams  of  the  potassium  soaps  look  at  the  end 
of  two  hours.  It  is  again  obvious  that  they  die  down  earlier 
in  the  series  of  the  potassium  soaps  than  in  the  corresponding 
sodium  soaps,  or,  put  another  way,  they  last  longest  in  the  higher 
members  of  the  potassium  soaps  and  at  the  lower  temperatures. 


146 


SOAPS  AND  PROTEINS 


FIGUBE83. 


~  •• " 


FIGURE  84. 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


147 


FIGURE  85. 


FIGURE  86. 


148 


SOAPS  AND  PROTEINS 


Fig.  87  illustrates  the  foaming  qualities  of  the  potassium  soaps 
of  the  acetic  series  in  the  concentration  m/2.     The  first  soap  to 


FIGURE  87. 


show  any  foaming  is  the  caprate,  but  its  foam  dies  down  completely 
in  two  hours,  as  shown  by  its  absence  in  the  series  of  tubes  marked 
8  of  Fig.  88.  It  will  be  observed  when  the  laurate,  myristate, 


THE  COLLOID-CHEMISTRY  OF  SOAPS  149 

palmitate  and  stearate  tubes  (the  series  9,  10,  11,  and  13  of  Fig. 
87)  are  compared  with  the  similarly  numbered  tubes  of  Fig.  85 
that  these  potassium  soaps  foam  decidedly  better  at  the  m/2 
concentration  than  at  the  higher  concentration.  The  foams  also 
last  well,  as  evidenced  when  Fig.  88  is  compared  with  Fig.  87. 
Fig.  88,  taken  two  hours  after  the  foaming  was  produced,  again 
shows  that  the  persistence  of  a  foam  rises  with  the  position  of  a 
soap  in  the  series  and  falls  with  increase  in  temperature,  once  the 


FIGURE  88. 

soap/water  systems  have  been  warmed  above  their  liquefaction 
points. 


150  SOAPS  AND  PROTEINS 

2.  The  Emulsifying  Properties  of  Soaps 

We  wish  now  to  discuss  the  relationship  which  exists  between 
the  emulsifying  properties  of  the  different  soaps  and  their  hydra- 
tion  capacity.  Excepting  as  the  concentration  necessary  for  emulsi- 
fication  is  different  (usually  higher)  the  same  general  truths  hold  for 
emulsification  previously  expressed  for  foaming. 

An  emulsion  is,  by  definition,  a  mixture  of  two  immiscible 
liquids  in  each  other.  But  from  any  two  liquids  such  as  oil  and 
water,  two  types  of  emulsion  may  be  prepared,  the  one  consisting 
of  a  subdivision  of  oil  in  water,  the  other  of  water  in  oil.  Milk, 
which  readily  mixes  with  water  and  wets  a  paper  dipped  into  it, 
may  be  cited  as  an  example  of  the  former.  Butter,  which  will 
mix  with  oil  but  not  with  water,  which  grease^  paper  and  imparts 
an  oily  feel  to  the  touch,  may  be  cited  as  an  example  of  the  latter. 
The  type  of  emulsion  important  for  an  analysis  of  the  emulsifying 
properties  of  the  ordinary  soaps  is  that  represented  by  the  sub- 
division of  oil  in  water. 

In  the  discussion  of  emulsification  we  must  also  distinguish 
between  (a)  the  mere  production  of  an  emulsion  and  (b)  its 
stabilization  after  production.  Just  as  in  the  case  of  foams,  the 
former  represents  essentially  a  mechanical  process — the  one 
liquid  must  by  some  means  or  other  be  divided  into  the  second. 
When  we  talk  about  emulsification  or  emulsifying  agencies  with- 
out modifying  clauses  we  usually  mean  methods  or  substances 
through  which  an  emulsion  produced  by  mechanical  means  may 
be  stabilized. 

It  has  been  shown  previously 1  that  an  oil  cannot  be  sub- 
divided permanently  into  pure  water,  and  that  the  so-called 
emulsifying  agents  which  make  possible  the  permanent  sub- 
division of  oil  in  water  are  hydrophilic  (lyophilic)  colloids.  Among 
the  best  representatives  of  this  group  are  the  soaps.  As  ordi- 
narily employed  for  emulsification  purposes  the  soaps  are,  of  course, 
mixed.  The  quantitative  studies  on  the  hydration  capacities  of 
the  different  pure  soaps  outlined  in  the  preceding  pages,  now 
allow  us  to  test  out  this  whole  concept  of  emulsification  more 
accurately.  What  is  the  relationship  between  the  hydrophilic 
properties  of  any  soap  and  its  emulsifying  power? 

1  MARTIN  H.  FISCHER  and  MARIAN  ().  HOOKKH:  Science,  43,  468  (1916); 
Kolloid-Zeitechr.,  18,  129  (1916);  Fats  and  Fatty  Degeneration,  New  York 
(1917). 


THE  COLLOID-CHEMISTRY^OF  SOAPS  151 

In  order  not  to  lengthen  this  discussion  unduly,  the  experi- 
mental facts  in  the  case  may  be  summed  up  as  follows:  those  soaps 
are  the  best  emulsifying  agents  which  at  the  temperature  of  their  use 
and  in  the  presence  of  water  yield  essentially  liquid  systems  of  the 
type  water-dissolved-^n-soap.  For  this  reason  the  oleates,  lino- 
lates,  etc.,  are,  of  all  the  soaps  studied,  the  best  emulsifiers  at 
ordinary  (room)  temperatures  because,  besides  having  high  hydra- 
tion  values,  they  are  liquid. 

The  sodium  soaps  of  the  acetic  acid  series  when  used  in  equi- 
molar  concentration  show  the  following  characteristics.  The  soaps 
of  the  lowermost  members  through  the  caproate  yield  no  perma- 
nent emulsions.  If  a  sodium  caprylate  or  sodium  caprate/ water 
system  is  kept  just  above  its  liquefaction  point,  a  permanent 
emulsion  may  be  obtained.  A  slight  rise  in  temperature,  how- 
ever, makes  for  separation  of  the  oil  from  the  water  phase.  The 
same  is  true  for  the  sodium  soaps  of  the  higher  fatty  acids.  At 
low  temperatures  sodium  myristate,  sodium  palmitate,  sodium 
stearate,  etc.,  in  water  do  not  emulsify,  but  if  the  temperature 
of  these  mixtures  is  raised  so  that  the  soaps  "  go  into  solution  " 
(in  reality  yield  liquid  colloid  systems  of  the  type  water-dissolved- 
in-soap)  permanent  emulsions  can  be  obtained  at  once.  With 
too  great  increase  in  temperature,  however,  the  emulsions  again 
crack,  and  the  oil  separates  off. 

In  interpretation  of  these  general  findings  it  may  be  said  that 
the  lowermost  soaps  do  not  emulsify  because  they  yield  only  true 
solutions  of  the  soaps  in  the  water.  The  systems,  in  other  words, 
have  no  hydrophilic  properties  or,  put  another  way,  the  water 
in  them  is  essentially  "  free  "  and  permanent  emulsification  of 
oil  in  such  "  free  "  water  cannot  be  obtained.  With  the  develop- 
ment of  distinctly  hydrophilic  properties  by  the  soaps  in  the  middle 
of  the  series  emulsification  becomes  possible,  but  only  while  the 
systems  are  liquid  and  of  the  type  water-dissolved-in-soap.  Only 
slight  further  increase  in  temperature,  however,  is  necessary  in 
the  case  of  soaps  like  the  caprylate  and  caprate  to  carry  them 
through  this  region  into  the  realm  of  the  true  solutions  of  soap 
in  water,  and  as  this  happens  permanent  emulsification  again 
becomes  impossible. 

Similar  facts  hold  for  the  soaps  of  the  higher  fatty  acids. 
An  oil  cannot  be  emulsified  in  any  of  these  higher  soaps  even 
when  possessed  of  a  high  hydration  capacity  as  long  as  they  are 


152 


SOAPS  AND  PROTEINS 


solid.  But  as  soon  as  the  temperature  is  raised  sufficiently  the  re- 
sulting liquid  colloid  systems  emulsify  splendidly.  The  matter  is 
illustrated  for  the  case  of  sodium  palmitate  in  the  right-hand  bottle 
of  Fig.  89.  In  this  60  cc.  cottonseed  oil  were  ground  into  20  cc. 


m/16  "  solution  "  of  the  soap  in  a  hot  water  bath.  At  this 
temperature  a  fine  emulsion  results.  As  soon,  however,  as  the 
temperature  is  allowed  to  drop  to  25°  for  a  few  hours  the  system 
cracks,  as  shown  in  the  left-hand  bottle  of  Fig.  89.  If,  however, 
the  temperature  is  maintained  above  the  liquefaction  point  of 


THE  COLLOID-CHEMISTRY  OF  SOAPS 


153 


the  sodium  palmitate/water  system,  permanent  emulsification 
results,  as  evidenced  in  the  right-hand  bottle  of  Fig.  89.  The 
higher  soaps,  moreover,  maintain  their  high  hydration  values  (as 
liquids)  through  a  considerable  range  of  temperature,  wherefore 


further  increase  in  temperature  does  not  serve  so  quickly  to  break 
an  emulsion  stabilized  in  these  higher  soaps  as  in  the  case  of  the 
lower  ones.  The  higher  soaps,  in  other  words,  do  not  pass  as 
quickly  as  the  lower  ones  into  the  class  of  the  true  solutions  of 
soap  in  water. 


154  SOAPS  AND  PROTEINS 

It  is  possible  to  test  out  these  general  notions  by  using  the 
potassium  soaps  instead  of  the  sodium  soaps  of  the  acetic  acid 
series.  The  potassium  soaps  being  in  general  more  soluble  in 
watej  and  more  nearly  liquid  at  a  given  temperature  than  the 
corresponding  sodium  soaps,  permanent  emulsification  requires 
either  (a)  a  higher  concentration  of  the  potassium  soap  or  (6) 
a  lower  temperature  or  (c)  a  soap  higher  in  the  series.  It  there- 
fore requires  more  of  a  soap  low  in  the  series  like  potassium  capry- 
late  or  caprate  to  the  unit  volume  of  water  to  yield  a  permanent 
emulsion.  The  emulsions  so  produced  also  break  easily  upon 
slight  increase  in  temperature.  On  the  other  hand,  the  potassium 
soaps  of  the  higher  fatty  acids,  which  in  the  presence  of  water 
yield  more  liquid  systems  even  at  ordinary  temperatures  than  the 
corresponding  sodium  soaps,  may  be  used  to  obtain  permanent 
emulsions  when  the  corresponding  sodium  soaps  will  not  act. 
Potassium  laurate,  myristate  or  palmitate  mixtures  with  water 
act  as  splendid  emulsifying  agents  at  low  temperatures  at  which 
the  corresponding  sodium  soaps  are  useless.  Even  potassium 
palmitate  acts  well  when  the  temperature  at  which  it  is  used 
lies  but  slightly  above  the  ordinary  room  temperature.  This 
is  illustrated  in  the  left-hand  bottle  of  Fig.  90.  The  potassium 
soaps  being  more  readily  soluble  in  water  than  the  corresponding 
sodium  soaps  with  increase  in  temperature,  the  fine  emulsion 
produced  in  hydrated  potassium  palmitate  cracks  as  soon  as  the 
temperature  is  raised  to  that  of  a  boiling  water  bath.  This  is 
shown  in  the  right-hand  bottle  of  Fig.  90.  In  this  experiment 
also,  60  cc.  cottonseed  oil  were  emulsified  in  20  cc.  m/16  potassium 
palmitate  by  grinding  in  a  mortar. 

3.  On  the  Theory  of  Foaming  and  Emulsification 

While  we  have  no  direct  interest  in  theories  of  foaming  and 
emulsification,  it  is  difficult  to  work  in  these  fields  without  inquir- 
ing into  the  nature  of  the  conditions  which  make  foaming  and 
emulsification  possible. 

It  would  seem  from  the  experiments  which  have  been  detailed 
above  and  in  our  previous  publications  on  emulsification  that 
permanent  foaming  or  emulsification  is  possible  only  as  the  liquid 
into  which  a  gas  or  a  second  liquid  is  dispersed  is  changed  from 
one  possessed  of  the  physico-chemical  constants  of  the  pure  dis- 


THE  COLLOID-CHEMISTRY  OF  SOAPS  155 

persion  medium  into  another  possessed  of  those  characteristic 
of  a  liquid  hydrated  colloid. 

From  a  gas  and  a  liquid,  as  from  two  immiscible  liquids,  it 
is  possible,  of  course,  to  produce  two  types  of  systems  represented 
in  the  first  instance  by  the  dispersion  of  a  gas  in  a  liquid  (a  foam) 
or  of  a  liquid  in  a  gas  (a  fog)  and  represented  in  the  second  instance 
by  the  dispersion  of  the  liquid  a  in  6  (as  oil  in  water)  or  the  dis- 
persion of  the  liquid  b  in  a  (as  water  in  oil).  When  one  regards 
as  a  whole  the  field  of  the  dispersoids  consisting  of  gas  plus  liquid 
and  similarly  that  of  the  dispersoids  consisting  of  liquid  in  liquid, 
one  is  quickly  struck  by  the  fact  that  lasting  dispersions  of  gas 
in  liquid  (foams)  can  be  more  readily  produced  than  the  opposite 
type  of  system;  while  certain  liquids  a  can  be  more  readily 
emulsified  in  a  second  b  than  vice  versa. 

In  trying  to  discover  what  is  the  first  general  relationship 
which  determines  this  behavior,  it  has  seemed  to  us  that  a  pre- 
viously expressed  opinion  1  covers  the  case  satisfactorily.  Other 
conditions  remaining  the  same,  that  material  is  dispersed  within 
any  second  which  in  response  to  mechanical  deformation  shows 
the  shorter  breaking  length.  Our  meaning  may  be  illustrated 
by  reference  to  'Figs.  91  and  92.  When  air  and  some  liquid 
like  liquid  hydrated  soap  are  subjected  to  a  deforming  move- 
ment (like  the  beat  of  a  flail)  it  is  obvious  that  the  gas 

OOO  OOO  OO  OOO  COO  —  -  Gas 


*  Hydrated  Sodium  Stearate 


FIGURE  92. 


will  "  break  "  sooner  than  the  liquid  columns  of  hydrated  soap. 
The  soap  will,  in  other  words,  be  drawn  into  longer  threads  or 
coherent  surfaces  than  will  the  air,  in  consequence  of  which 
the  gas  will  become  enmeshed  within  the  hydrated  colloid,  and 
a  foam  will  result. 

What  happens  in  the  case  of  two  liquids  is  represented  diagram- 
matically  in  Fig.  92.  If  the  middle  line  of  the  diagram  is  taken 

1  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Fats  and  Fatty  Degen- 
eration, 32,  New  York  (1917). 


156  SOAPS  AND  PROTEINS 

to  represent  the  breaking  length  of  oil  threads,  the  breaking  length 
of  a  soap,  like  hydrated  sodium  oleate,  is  represented  by  the  lower 
line  of  the  diagram.  For  this  reason,  other  things  being  equal, 
the  oil  tends  to  break  into  droplets  sooner  than  the  hydrated 
sodium  oleate  which  in  consequence  remains  the  non-dispersed 
or  enveloping  phase.  There  are,  however,  other  soaps  which, 
while  capable  of  hydration,  yield  liquids  whose  fibers  tend  to 
break  sooner  when  drawn  into  threads  than  does  hydrated  sodium 
oleate,  or  which  at  the  ordinary  temperatures  employed  are  so 
nearly  solid  that  they  break  into  short  fragments.  Magnesium 
oleate,  sodium  stearate,  etc.,  may  be  cited  as  hydrated  soaps  of 
this  type.  Their  breaking  length  may  be  represented  diagram- 
matically,  as  compared  with  the  breaking  length  of  an  oil,  by 
the  upper  line  of  Fig.  92.  Other  things  being  equal,  these  materi- 
als, therefore,  tend  to  become  enmeshed  within  the  oil,  yielding, 
in  other  words,  emulsions  of  the  type  water-in-oil. 

The  experiments  detailed  above,  in  which  were  compared 
the  emulsifying  properties  of  different  soaps  (like  sodium  palmi- 
tate  and  potassium  palmitate.  sodium  stearate  and  potassium 
stearate)  or  the  behavior  of  these  soap/ water  systems,  when 
subjected  to  heat  manipulation,  prove  the  truth  of  this  general 
contention.  We  have  also  tried  to  measure  the  breaking  length 
of  the  different  systems  which  may  be  used  successfully  for  the 
production  of  foams,  fogs  or  the  two  types  of  emulsions.  We 
hope  to  be  able  to  detail  numerical  values  covering  these  points 
at  another  tune.  The  so-called  "  finger  tests  "  of  the  glue  tech- 
nologists permit  one  to  predict  what  kind  of  system  is  most  likely 
to  result  from  dispersion  in  each  other  of  a  gas  with  a  liquid  or  a 
liquid  with  a  liquid. 

We  are  not  unconscious  of  the  fact  that  there  may  be  arranged 
under  this  conception  many  of  the  so-called  theories  of  foaming 
and  emulsification  adduced  to  explain  the  behavior  of  these 
systems.  As  previously  emphasized  1  there  is  nothing  mutually 
exclusive  in  the  ideas  of  solvation  and  the  relative  breaking  lengths 
of  any  two  materials,  and  the  changes  in  surface  tension  and 
viscosity,  the  quantitative  relationship  between  the  amounts  of 
the  two  phases,  the  formation  of  a  continuous  third  phase  between 
the  two  general  substances  making  up  a  foam  or  an  emulsion,  the 

1  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Fats  and  Fatty  Degen- 
eration, 29,  New  York  (1917). 


THE  COLLOID-CHEMISTRY  OF  SOAPS  157 

"  surface  activity  "  of  various  chemical  substances  in  permitting 
the  "  wetting  "  of  contiguous  phases,  etc.,  as  drawn  upon  by 
various  authors  (S.  PLATEAU/  G.  QuiNCKE.2  F.  G.  DoNNAN,3 
H.  W.  HiLLYER,4  WALTHER  OsTWALD,5  T.  B.  ROBERTSON,6  S.  U. 
PICKERING,7  UBBELOHDE  and  GOLDSCHMIDT,S  WILDER  D.  BAN- 
CROFT,9 G.  H.  A.  CLOWES,I()  S.  A.  SHORTER  n  and  JAMES  W. 
McBAiN  12)  to  explain  the  nature  of  foaming  and  emulsification. 
When  water  is  changed  to  a  liquid  colloid  hydrate,  the  properties 
of  the  second  are  still  the  properties  of  a  liquid,  though  quantita- 
tively different  from  the  first,  and.  these  properties  include  surface 
tension,  viscosity,  distribution  of  dissolved  and  suspended  parti- 
cles, etc.  But  were  we  to  express  a  critical  opinion  of  the  theories 
of  foaming  and  emulsification  as  developed  by  these  various 
authors,  we  would  say  that  each  has  failed  in  the  opinion  of  some 
other  author  because  he  has  used  his  theory  as  an  exclusive  one 
and  as  one  necessarily  universally  applicable.  As  we  have  repeat- 
edly emphasized,  a  number  of  factors  undoubtedly  play  a  role, 
and  the  relative  importance  of  each  varies  not  only  in  different 
foams  and  in  different  emulsions  but  in  one  and  the  same  foam 
or  emulsion  under  different  circumstances. 

4.  The  Washing  Properties  of  Soaps 

Empiric  practice  seems  to  have  succeeded  in  furnishing  soaps 
of  good  washing  properties  for  almost  all  technologic  needs  and 
for  use  under  the  most  varied  circumstances,  and  this  in  spite 
of  the  fact  that  we  seem  still  to  be  largely  ignorant  of  why  in 

!S.  PLATEAU:  Ann.  der.  Physik.,  141,  44  (1870). 

2  G.  QUINCKE:  Ann.  der  Physik.,  271,  580  (1888). 

3  F.  G.  DONNAN:  Zeitschr.  f.  physik.  Chem.,  31,  42  (1899). 

4H.  W.  HILLYER:  Jour.  Am.  Chem.  Soc.,  25,  511  (1903);  ibid.,  25,  524 
(1903). 

5  WALTHER  OSTWALD:  Kolloid-Zeitschr.,  6,  103  (1910);  ibid.,  7,  64  (1910). 
6T.  B.  ROBERTSON:  Kolloid-Zeitschr.,  7,  7  (1910). 
7S.  U.  PICKERING:    Kolloid-Zeitschr.,  7,  15  (1910). 

8  UBBELOHDE  and  GOLDSCHMIDT:   Handbuch  der  Oele  und  Fette,  3,  11, 
Leipzig  (1910);   Zeitschr.  f.  Elektrochem.,  18,  380  (1912);   Kolloid-Zeitschr., 
12,  18  (1913);  Kolloidchem.  Beihefte,  5,  427  (1914). 

9  WILDER  D.  BANCROFT:  Jour.  Physical  Chem.,  17,  501  (1913). 

10  G.  H.  A.  CLOWES:  Jour.  Physical  Chem.,  20,  415  (1916). 

11  S.  A.  SHORTER:  Jour.  Soc.  Dyers  and  Colorists,  32,  99  (1916). 

12  JAMES  W.  McBAiN  and  C.  S.  SALMON:   Jour.  Am.  Chem.  Soc.,  42,  426 
(1920). 


158  SOAPS  AND  PROTEINS 

actual  use  the  soaps  act  as  they  do.  The  following  paragraphs 
do  not  pretend  to  bring  a  definitive  answer  to  the  problem,  but 
in  connection  with  the  remarks  of  the  preceding  paragraphs  it 
has  seemed  to  us  that  they  may  help  toward  a  formulation  and 
solution  of  some  of  the  general  problems  involved. 

The  oldest,  perhaps,  of  the  theories  of  washing  holds  that 
soap  owes  its  cleansing  virtues  to  the  alkali  which  it  liberates  on 
solution  in  water.  This  factor  as  an  important  item  in  the  wash- 
ing process  has  been  much  discredited.  While  it  is  not  to  be 
denied  that  its  importance  was  formerly  overestimated,  it  is 
perhaps  too  extreme  to  deny  it  all  virtue.  The  fact  that  even 
soft  water  alkalinized  through  the  addition  of  sodium,  potassium 
or  ammonium  hydroxid,  sodium  carbonate  or  borax  washes  better 
than  the  water  alone  would  seem  to  make  it  impossible  to  deny 
the  virtue  of  this  factor  entirely. 

On  the  other  hand,  the  alkali  factor  cannot  be  the  main 
feature  which  gives  soap  its  washing  properties,  for  the  very 
soaps  which  on  hydrolysis  yield  the  largest  overplus  of  free  alkali, 
namely,  the  soaps  of  the  highest  fatty  acids,  may  wash  most 
poorly.  On  the  other  hand,  soaps  which  by  test  and  under  the 
circumstances  of  their  use  are  strictly  neutral  may  function  as 
ideal  cleansers.  To  explain  the  action  of  soap  Under  such  cir- 
cumstances, its  power  to  produce  foams  and  to  emulsify  has  been 
called  into  account,  and  this  property  has  been  paralleled  with 
its  cleansing  virtues.  If  this  conception  is  correct — and  there 
is  much  to  support  the  idea  that  it  represents  the  major  factor 
in  the  general  washing  power  of  the  soaps — then  the  value  of  dif- 
ferent common  soaps  as  generally  employed  would,  on  the  basis 
of  our  previous  remarks,  be  about  as  follows: 

To  produce  effective  cleansing  a  certain  minimum  of  mechanical 
washing  methods  are  absolutely  necessary.  The  soiled  materials 
must  be  "  soused  "  in  the  wash  water,  rubbed  on  a  washboard 
or  dragged  about  in  a  machine.  This  constitutes  in  the  washing 
process  the  equivalent  of  the  mechanical  element  so  necessary  for 
the  production  of  foams  and  emulsions.  The  "  dirt "  in  the 
clothes  is  emulsified  in  the  hyd rated  soap  of  the  wash  water. 

The  soap  must  now  be  looked  at  from  the  point  of  view  of 
favoring  such  emulsification  and  the  stabilization  of  the  emulsion 
after  production.  Obviously,  of  much  importance  in  this  matter 
will  be  (a)  the  concentration  at  which  the  soap  is  used,  (6)  the 


THE  COLLOID-CHEMISTRY  OF  SOAPS  159 

character  of  the  soap  and  (c)  the  temperature  at  which  it  is 
employed. 

It  is  the  common  practice  to  rub  solid  or  semi-solid  soap  directly 
upon  the  soiled  materials  or  to  soak  them  in  a  strong  soap  stock. 
Even  after  such  soaking,  more  solid  or  semi-solid  soap  is  com- 
monly rubbed  directly  upon  the  more  soiled  areas.  This  is  all 
expressive  of  the  need  for  a  hydrated  colloid  of  high  concentration, 
for  only  such  will  lead  to  easy  and  permanent  stabilization  of  the 
"  dirt "  (fatty  materials  and  mixed  solids)  in  emulsified  form  in 
the  "  soap  water." 

The  ordinary  washing  soaps  (either  laundry  or  toilet)  are 
the  sodium  soaps  of  several  fatty  acids.  It  is  of  interest  to  note 
that  manufacturers  have  long  used  mixtures  of  different  fats  for 
their  soap  stocks.  Beginning  as  they  usually  do  with  a  liquid 
fat  (like  cocoanut  oil,  olive  oil,  cottonseed  oil)  they  add  to  this 
varying  amounts  of  the  higher  fats  (like  tallow,  hydrogenated 
cottonseed  oil,  etc.).  The  ultimate  soap  produced  contains  a 
long  and  varied  list  of  fatty  acids.  Such  mixtures  must  obviously 
satisfy  most  general  needs.  Because  of  the  presence  of  soaps 
of  the  lowermost  fatty  acids,  quick  foaming  and  quick  emulsi- 
fication  are  obtained  even  at  low  temperatures.  These  lower- 
most soaps,  however,  dissolve  so  quickly  that  the  frugal  house- 
wife considers  them  wasteful.  Especially  is  this  the  case  when 
the  soaps  are  used  with  hot  water  in  which  they  pass  quickly 
into  the  "  true  solution  "  stage.  For  this  reason  the  presence 
of  fatty  acid  soaps  from  the  middle  of  the  series  will  prove  useful, 
for  these  work  well  in  ordinary  "  lukewarm  "  waters.  They  too, 
however,  lose  much  of  their  virtue  if  the  temperature  is  raised. 
As  effectively  working  soaps  in  waters  near  the  boiling  point, 
the  soaps  of  the  higher  fatty  acids  are  required.  The  palmitates 
and  stearates,  for  example,  still  maintain  their  colloid  character- 
istics when  soaps  lower  in  the  series  have  lost  theirs  through 
"  solution." 

The  facts  recited  indicate  why  the  temperature  at  which 
any  soap  is  used  has  so  much  to  do  with  its  effectiveness.  Where 
soaps  are  to  be  used  in  cold  water,  it  is  clear  that  none  of  the 
higher  fatty  acid  soaps  are  of  any  particular  use.  Only  those 
soaps  which  at  low  temperatures  have  definitely  colloid  character- 
istics, and  which  as  ordinarily  employed  yield  liquid  colloid 
systems,  are  effective  for  washing  under  such  circumstances. 


160  SOAPS  AND  PROTEINS 

This  is  the  reason  why  sodium  and  potassium  oleate  and  the 
soaps  made  from  oils  rich  in  the  lower  fatty  acids  (cocoanut  oil 
soap,  palm  kernel  oil  soap)  are  the  soaps  which,  above  all  others, 
are  held  useful.  On  the  other  hand,  for  warmer  waters  it  is  of 
advantage  to  have  present  the  soaps  of  the  fatty  acids  higher  in 
the  series.  Hence  the  common  practice  of  adding  tallow,  hydro- 
genated  cottonseed  oil,  etc.,  to  the  more  liquid  fats  and  oils 
used  for  the  manufacture  of  toilet  and  laundry  soaps  in  "  civilized  " 
countries.  There  is,  however,  a  limit  at  this  end  of  the  series 
also.  The  sodium  soaps  above  the  stearate  in  the  acetic  series 
do  not  yield  (liquid)  hydrated  colloid  systems  below  the  boiling 
point  of  water.  In  this  proportion  they  are  valueless  as  wash- 
ing agents.  Even  the  stearate  which,  since  the  introduction 
of  hydrogenation  methods,  has  been  worked  in  increasing 
amounts  into  the  common  toilet  and  laundry  soaps  already  comes 
close  to  the  danger  line.  It  will  hardly  foam  or  emulsify  short 
of  the  boiling  point  of  water.  A  way  out  of  the  difficulty,  not 
only  for  the  stearate,  but  also  for  some  of  the  other  higher  fatty 
acids,  may  be  found  in  the  substitution  of  potassium  for  the 
sodium  of  the  common  soaps.  This  trick  is  employed  in  "  shaving 
soaps  "  in  which  the  waste  of  a  more  "  soluble  "  soap  is  compen- 
sated for  by  its  readier  foaming  and  emulsifying  properties.  But 
the  substitution  of  potassium  for  sodium  has  its  defects  at  the 
lower  end  of  the  -series — the  potassium  soaps,  being  more  readily 
"  soluble  "  both  in  cold  and  hot  waters,  pass  too  quickly  through 
their  working  middle  of  liquid  hydrated  colloids  and  hence  are 
"  wasteful." 


PART  TWO 
THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE 


PART  TWO 
THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE 


PRINCIPLES  OF  HOT  AND   COLD  PROCESS  SOAP 
MANUFACTURE 

1.  Introduction 

IT  will  be  the  purpose  of  this  chapter  to  review  certain  tech- 
nical procedures  followed  in  soap  manufacture  in  order  to  see 
where  the  concepts  developed  in  the  preceding  pages  may  be 
used  as  conscious  substitutes  for  various  empiric  practices.  In 
doing  so  we  will  be  struck  by  an  interesting  fact.  Faced  on  the 
one  side  by  the  myriad  problems  incident  to  the  handling  of  a 
widely  varying  crude  material  and  on  the  other  by  the  demands 
on  the  part  of  the  public  for  a  product  possessed  of  certain  washing 
characteristics,  the  practical  soap  manufacturer  has  in  nearly 
every  instance  hit  upon  both  a  satisfactory  process  and  a  satis- 
factory product. 

The  raw  materials  used  by  the  soap  chemist  and,  consequently, 
the  soaps  which  he  produces  are  so  many  and  so  various  that  a 
complete  review  of  the  situation  is  not  possible.  What  is  said 
in  the  following  pages  represents  little  more  than  a  broad  outline. 

We  should  have  an  ideal  starting  point  did  we  know,  as  a 
first  foundation  for  our  discussion,  the  qualitative  and  quantita- 
tive composition  of  the  fats  and  oils  which  enter  the  soap  kettle. 
Even  when  we  ignore  the  presence,  in  the  crude  fats  and  oils 
employed,  of  unsaponifiable  material,  of  alcohols  other  than 
glycerin,  of  admixed  substances  bearing  no  relationship  to  the 
esters  which  make  up  the  mass  of  the  fat  or  oil,  etc.,  we  are  still 
handicapped  by  an  inadequate  knowledge  of  the  complete  com- 

163 


164  SOAPS  AND  PROTEINS 

position  of  even  the  commoner  fats  and  oils.  Or,  where  such 
complete  analyses  have  been  made  or  are  available,  they  refer, 
of  course,  only  to  a  specific  sample  and,  as  every  oil  and  fat 
chemist  knows,  another  sample  obtained  presumably  from  the 
same  sources  and  under  the  same  conditions  may  still  show  wide 
variations  in  composition.  A  single  fat  or  oil  varies  for  example 
with  the  seasons. 

It  lies  without  the  limits  of  this  volume  to  list  more  than  a 
few  of  the  fats  and  oils  which  have  been  or  may  be  used  in  the 
manufacture  of  soaps  and  to  indicate  their  approximate  compo- 
sition. The  examples  which  follow  are  of  interest  either  because 
they  furnish  much  of  the  material  which  is  used  in  soap  manu- 
facture or  because  their  qualitative  composition  is  such  that 
they  yield  soaps  with  qualifications  of  interest  to  our  discussion 

2.  The  Oils,  Fats  and  Waxes  Entering  the  Soap  Kettle 

From  a  purely  chemical  point  of  view  there  is  little  reason  to 
distinguish  between  the  "  oils  "  and  the  "  fats  "  of  the  technical 
chemists;  and  the  same  is  true  of  the  "  waxes."  All  three  sub- 
stances are  essentially  nothing  but  mixtures  of  different  esters. 
In  the  case  of  the  oils  and  fats  these  are  almost  exclusively  glycer- 
ids,  and  this  still  holds  true  for  many  of  the  waxes  (as  "  Japan 
wax  ").  At  other  times  the  waxes  are  still  esters,  but  some  other 
alcohol  may  have  taken  the  place  of  the  glycerin.  Nevertheless, 
this  practical  distinction  between  the  three  groups  of  substances — 
the  first  being  liquid  at  ordinary  temperatures,  the  second  semi- 
solid  or  solid,  the  third  definitely  solid — has  some  value.  The 
physical  state  parallels  roughly  the  kinds  and  proportions  of  different 
fatty  adds  appearing  in  the  various  esters,  the  fatty  adds  with  the 
lower  melting  points  being  those  most  common  in  the  oils  while  those 
with  the  higher  melting  points  predominate  in  the  fats  and  waxes. 
This  matter  is  of  much  importance,  as  will  appear  later,  because 
of  the  physico-chemical  differences  in  the  soaps  which  are  formed 
from  these  different  stocks. 

A  distinction  in  soap  manufacture  between  the  fats  of  vege- 
table and  those  of  animal  origin  has  little  purpose,  for  both  con- 
tain qualitatively  the  same  list  of  glycerids.  Nevertheless  it  is 
well  to  remember  that  the  two  different  origins  may  at  times  be 
of  importance  because  of  differences  in  the  types  of  impurities 
which  they  bring  along. 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    165 

Since  the  kind  of  soap  formed  and  its  properties  are  so  largely 
a  matter  of  the  kind  and  relative  proportion  of  the  fatty  acids 
which  occur  in  the  original  soap  stock  it  is  well  to  begin  by  listing 
a  few  of  the  commoner  oils,  fats  and  waxes  and  giving  their  per- 
centage composition.  The  series  which  follows  is  catalogued 
arbitrarily,  those  fats  which  contain  the  smallest  number  of  fatty 
acids  or  such  as  have  the  lower  melting  points  being  given  first. 
A  more  detailed  discussion  of  this  subject  lies  without  the  limits 
of  this  volume;  for  such  the  accepted  handbooks  l  or  original 
papers  dealing  with  this  subject  must  be  consulted. 

Linseed  Oil.  A  generally  accepted  average  analysis  is  that 
of  HAZURA  and  GRUSSNER  which  reads  as  follows: 

Oleic  acid 5  percent 

Linolic  acid 15  percent 

Linolenic  acid 15  percent 

"  Isolinolenic  "  acid 65  percent 

In  the  place  of  the  above  analysis,  to  which  J.  LEWKOWITSCH  2 
has  raised  objection,  this  author  gives  the  following: 

Solid  fatty  acids  (palmitic,  myristic,  stearic,  arachidic) .     7.5  percent 

Linolic  acid 36 . 5  percent 

Linolenic  acid 56 . 0  percent 

Poppy  Seed  Oil.  The  whole  oil  carries  6.67  percent  of  solid 
fatty  acids  (TOLMAN  and  MuNSON3).  The  liquid  fatty  acids 
consist,  according  to  HAZURA  and  GRUSSNER,  of 

Oleic  acid 30  percent 

Linolic  acid 65  percent 

Linolenic  acid 5  percent 

Cottonseed  Oil.  According  to  TWITCHELL,  FARNSTEINER,  TOL- 
MAN and  MuNSON,4  the  whole  oil  contains  from  22.3  to  32.6  per- 
cent of  solid  fatty  acids,  consisting  chiefly  of  palmitic  acid  with 
a  small  quantity  of  arachidic  acid.  The  liquid  fatty  acids,  accord- 

1  See  for  example  J.  LEWKOWITSCH:   Oils,  Fats  and  Waxes,  5th  Ed.,  2, 
London  (1914) ;  MERKLEN:  Etude  sur  la  constitution  des  savons  du  commerce, 
Marseilles  (1906)  or  in  German  translation  by  FRANZ  GOLDSCHMIDT,  Halle  a/S 
(1907);  UBBELOHDE-GOLDSCHMIDT:  Handbuch  der  Oele  und  Fette,  Leipzig 
(1910). 

2  J.  LEWKOWITSCH:  Oils,  Fats  and  Waxes,  5th  Ed.,  2,  61,  London  (1914). 

3  L.  M.  TOLMAN  and  L.  S.  MUNSON:  Jour.  Am.  Chem.  Soc.,  25,  960  (1903). 

4  Quoted  by  J.  LEWKOWITSCH:    Oils,  Fats  and  Waxes,  5th  Ed.,  2,  197, 
London  (1914). 


166  SOAPS  AND  PROTEINS 

ing  to  HAZURA,  consist  approximately  of  40  percent  oleic  acid 
and  60  percent  linolic  acid. 

Sesame  Oil  This  oil  contains,  according  to  FARNSTEINER,  12.1 
to  14.1  percent  of  solid  acids,  the  liquid  acid  making  up  the 
remaining  fraction  holding  usually  about  15.8  percent  linolic  acid 
and  72.1  percent  oleic  acid. 

Olive  Oil.  According  to  TOLMAN  and  MUNSON/  the  solid 
fatty  acids  of  this  oil,  as  obtained  from  different  sources,  vary 
between  2  and  17.72  percent.  These  solid  fatty  acids  are  chiefly 
palmitic  acid  with  a  trace  of  arachidic.  Stearic  acid  is  absent. 
The  liquid  fatty  acids,  according  to  HAZURA  and  GKUSSNER, 
consist  of  93  percent  oleic  acid  and  7  percent  linolic  acid. 

Castor  Oil.  The  whole  oil  on  standing  in  the  cold  deposits 
3  to  4  percent  of  stearic  and  ricinoleic  acids  (KRAFFT2)  and  1 
percent  dihydroxystearic  acid  (JUILLARD).  The  liquid  fatty  acids 
of  castor  oil  consist  chiefly  of  ricinoleic  and  some  isoricinoleic 
acid.  Oleic  acid  seems  to  be  absent  (HAZURA  and  GRUSS- 

NER3). 

Cod  Liver  Oil.  Crude  cod  liver  oil  contains  a  considerable 
portion  of  stearic  and  palmitic  acids.  The  oil  as  it  comes  to 
market  has  usually  been  freed  from  these.  In  the  liquid  oil 
small  quantities  of  acetic,  butyric,  valeric  and  capric  acids  have 
been  found  by  various  authors.  There  is  an  absence  of  oleic 
acid,  and  it  is  believed  that  the  bulk  of  the  fatty  acids  is  made 
up  of  acids  less  saturated  than  those  of  the  oleic  acid  series. 
According  to  HEYERDAHL  4  the  following  percentages  of  different 
acids  have  been  definitely  isolated. 

Palmitic  acid 4  percent 

Jecoleic  acid 20  percent 

Therapic  acid 20  percent 

Palm  Oil.  This  is  a  mixture  of  glycerids  of  oleic  acid  and 
various  solid  fatty  acids.  Ninety-eight  percent  of  the  solid  fatty 
acids  is  palmitic  acid  and  1  percent  or  less  is  stearic  acid.  HAZURA 
and  GRUSSNER  have  discovered  linolic  acid  among  the  Ifquid 
fatty  acids  of  this  oil. 

1  L.  M.  TOLMAN  and  L.  S.  MUNSON:  Jour.  Am.  Chem.  Soc.,  25,  95(>  (1903). 
*F.  KRAFFT:   Ber.  d.  deut.  chem.  Gesellsch.,  21,  2730  (1888). 
1  Quoted  by  J.  LEWKOWITSCH:    Oils,  Fats  and  Waxes,  5th  Ed.,  2,  ms, 
London  (1914). 

4  J.  LEWKOWITSCH:  Oils,  Fats  and  Waxes,  5th  Ed.,  2,  430,  London  (1914). 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    167 

Nutmeg  Butter.  The  composition  of  this  fat  is  thus  sum- 
marized by  J.  LEWKOWITSCH.1 

Myristic  acid 73      percent 

Oleic  acid ' 3      percent 

Linolenic  acid .5  percent 

Formic,  acetic,  cerotic  acids small  amounts 

Essential  oil 12 . 5  percent 

Unsaponifiable  and  resinous  material 10 . 5  percent 

Cacao  Butter.  This  fat  contains  stearic  acid  to  an  extent  of 
about  40  percent.  Oleic  acid  is  present  in  excess  of  30  percent. 
Several  other  fatty  acids  have  been  declared  to  be  present ,  but 
their  amounts  are  debated.  Palmitic,  arachidic  and  linolic  acids 
have  been  found  and,  according  to  debatable  evidence,  lauric 
and  caprylic  are  also  present. 

Palm  Kernel  Oil.  This  interesting  and  much  used  fat,  accord- 
ing to  ELSDON  2  is  composed  of  the  following : 

Caproic  acid 2  percent 

Caprylic  acid 5  percent 

Capric  acid 6  percent 

Lauric  acid 55  percent 

Myristic  acid 12  percent 

Palmitic  acid 9  percent 

Stearic  acid 7  percent 

Oleic  acid 4  percent 

Palm  kernel  oil  is  largely  used  for  soap  making,  chiefly  in  admix- 
ture with  other  oils  and  fats.  Like  cocoanut  oil,  it  is  eminently 
suitable  for  the  manufacture  of  soaps  by  the  "  cold  "  process. 
The  freshest  oil  is  employed  in  the  manufacture  of  vegetable  butter. 
Cocoanut  Oil.  J.  LEWKOWITSCH  uses  the  analysis  of  the  fatty 
acids  of  cocoanut  oil  by  PAULMYEB  to  produce  the  following  table: 

Caproic  acid 0 . 25  percent 

Caprylic  acid 0 . 25  percent 

Capric  acid 19 . 50  percent 

Lauric  acid 40 . 0    percent 

Myristic  acid 24 . 0    percent 

Palmitic  acid 10 . 6    percent 

Oleic  acid 5.4    percent 

1  J.  LEWKOWITSCH:  Oils,  Fats  and  Waxes,  5th  Ed.,  2,  564,  London  (1914). 

2  Quoted  by  J.  LEWKOWITSCH:    Oils,  Fats  and  Waxes,  5th  Ed.,  2,  621, 
London  (1914). 


168  SOAPS  AND  PROTEINS 

LEWKOWITSCH  adds  that  the  quantities  of  oleic,  caproic  and 
caprylic  acids  in  this  analysis  are  undoubtedly  too  low.  An 
analysis  by  ELSDON  showed  the  following: 

Caproic  acid • 2  percent 

Caprylic  acid 9  percent 

Capric  acid 10  percent 

Laurie  acid 45  percent 

Myristic  acid 20  percent 

Palmitic  acid 7  percent 

Stearic  acid 5  percent 

Oleic  acid 2  percent 

LEWKOWITSCH  holds  that  the  oleic  acid  figure  in  this  analysis  is 
also  too  low  while  that  of  stearic  acid  is  much  too  high. 

Japan  Wax.  (Japan  tallow).  The  important  fatty  acid  con- 
stituent of  this  wax  is  palmitic  acid.  Among  other  acids,  stearic, 
arachidic  and  oleic  are  said  to  be  present.1 

Goose  Fat.  This  fat  consists  essentially  of  oleic,  palmitic  and 
stearic  acids.  There  are  present  also  small  quantities  of  the 
lower  volatile  acids. 

Hog  Fat.  According  to  ERNST  TwrrcHELL2  lard  consists  of 
the  following: 

Linolic  acid 10 . 06  percent 

Oleic  acid 49 . 39  percent 

Solid  acids  (by  difference) 40 . 55  percent 

It  is  possible  that  linolenic  acid  is  also  present.  In  the  group 
of  the  solid  acids  are  lauric,  myristic,  palmitic  and  stearic. 

Tallow.  Tallow  is  essentially  a  mixture  of  palmitic,  stearic, 
and  oleic  acids.  According  to  an  examination  by  LINK  in  the 
laboratory  of  J.  LEWKOWITSCH  3  there  are  present  23.2  percent 
stearic  acid,  28.4  percent  palmitic  acid  and  48.4  percent  oleic 
acid.  It  is  possible  that  traces  of  other  acids  like  linolenic  also 
appear  in  tallow. 

Butter  fat.  The  following  acids  have  been  identified  in  butter 
fat:  acetic  (?),  butyric,  caproic,  caprylic,  capric,  lauric,  myristic, 
palmitic,  stearic,  arachidic  and  oleic  acids.  It  is  held  by  certain 
authors  that  butter  fat  also  contains  hydroxylated  acids.  The 
presence  of  linolenic  acid  has  been  described.  The  percentages 

1  J.  LEWKOWITSCH:  Oils,  Fats  and  Waxes,  5th  Ed.,  2,  654,  London  (1914). 

*E.  TWITCHKLL:  Jour.  Soc.  Chem.  Industry,  515  (1895). 

*  J.  LEWKOWITSCH:  Oils,  Fats  and  Waxes,  5th  Ed.,  2,  767,  London  (1914). 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    169 

of  the  glycerids  of  the  different  fatty  acids  are  as  indicated  in  the 
following  table,  copied  from  LEWKOWITSCH. 


Glycerids. 


J.  BELL. 


W.  BLYTH. 


SPALT.ANZANI.* 


Butyrin 

7  012 

7  7 

5  080 

Caproin  
Caprylin  and  caprin  
Olein  

I    2.280 

37  .  730 
52  978 

}o, 

42.2 
50  0 

1.020 
0.307 

}    93.593 

100 

100 

100 

*SPALLANZANJ:    Le  Staz.  Sperim.  Hal.,  23,  417  (1890). 

Beeswax  consists  chiefly  of  free  cerotic  acid  with  a  small 
quantity  of  free  mellisic  acid  and  small  quantities  of  unsaturated 
fatty  acids  combined  with  alcohols.  Ceryl  alcohol  appears  free 
in  beeswax.  Beeswax  contains  little  or  no  glycerin,  other  alcohols 
taking  its  place. 

3.  Significance  of  Some  Fat  and  Oil  Constants  for  the 
Colloid-Chemistry  of  Soap 

Since  complete  analyses  of  the  fats  and  oils  which  enter  the 
soap  chemist's  kettle  can  scarcely  be  obtained,  he  must  content 
himself  in  routine  practice  with  a  knowledge  of  their  specific 
gravity,  melting  point,  saponification  value,  REICHERT-MEISSL 
value,  iodin  number,  etc.  For  the  non-technically  trained,  the 
meaning  of  these  values  and  their  probable  significance  indeter- 
mining  in  advance  the  colloid  properties  of  the  resultant  soaps 
when  more  complete  analyses  of  the  fat  are  missing  are  appended. 

Since  the  natural  oils  and  fats  are  not  definite  chemical  sub- 
stances characterized  by  definite  melting  points,  it  becomes 
readily  intelligible  why  discordant  results  are  obtained  by  any 
of  the  number  of  methods  available  for  the  determination  of  the 
melting  points  of  oils  and  fats.  In  general,  however,  it  may  be 
said  that  the  lower  the  melting  point  of  a  fat  or  oil,  the  higher 
the  proportion  in  it  of  the  lower  melting  point  fatty  acids,  like 
the  oleates,  linolates  or  lower  members  of  the  acetic  series. 

The  specific  gravity  of  any  pure  fat  falls  in  any  series  with 
rise  of  the  fatty  acid  in  that  series.  Wide  differences,  however, 
exist  between  the  specific  gravities  of  the  fatty  acids  of  different 
series.  It  is  difficult  for  this  reason,  to  find  any  relationship 


170  SOAPS  AND  PROTEINS 

between  the  specific  gravity  of  mixed  glycerids  and  the  type  of 
fatty  acids  found  in  the  glycerids.  In  general,  however,  the 
lower  the  specific  gravity  of  a  fat  the  more  likely  it  is  to  be  found 
rich  in  the  higher  members  of  any  fatty  acid  series. 

The  saponification  value  of  an  oil,  fat  or  wax  which  indicates 
the  number  of  milligrams  of  potassium  hydroxid  required  for  the 
complete  saponification  of  one  gram  of  the  oil,  fat  or  wax  is  indica- 
tive of  the  amount  of  potassium  hydroxid  required  to  neutralize 
completely  the  fatty  acids  in  that  oil,  fat  or  wax.  Other  things 
being  equal,  a  high  saponification  value  therefore  means  a  high 
content  of  the  lower  fatty  acids. 

The  REICHERT-MEISSL  value  which  shows  the  number  of 
cubic  centimeters  of  decinormal  potash  required  to  neu- 
tralize that  portion  of  the  volatile  fatty  acids  which  is  obtained 
from  2.5  grams  of  a  fat  after  distillation  by  the  REICHERT  process, 
represents,  obviously,  the  proportion  of  volatile  fatty  acid  con- 
tained in  any  mixed  fat  most  likely  to  yield  soaps  lying  within 
the  range  of  those  commonly  used  for  washing  purposes. 

The  iodin  value  of  a  fat  or  fatty  acid  is  a  measure  of  the  pro- 
portion of  unsaturated  fatty  acids  contained  therein.  It  may  be 
used  as  an  index,  in  comparative  studies,  to  the  probable  pro- 
portion of  the  unsaturated  fatty  acids  present  in  any  oil,  fat  or 
wax  to  those  of  the  saturated  fatty  acids  and,  by  inference,  of 
the  proportion  of  the  soaps  of  these  two  series  of  fatty  acids  with 
their  varying  physico-chemical  or  colloid-chemical  constants  pro- 
ducible from  the  original  material. 

4.  Hot  and  Cold  Process  Soap  Manufacture 

As  familiarly  known,  soap  manufacture  may  be  carried  "on 
by  either  (a)  the  cold  process  or  (6)  the  hot  process.  So  far 
as  the  chemistry  is  concerned  the  two  are  supposed  to  yield  the 
same  result.  In  either  case,  a  weighed  amount  of  fat  or  oil  has 
added  to  it  the  amount  of  caustic  soda  which  analysis  has  shown 
the  fat  to  require  for  conversion  into  neutral  soap.  What  is 
obtained  in  the  end  is  a  neutral  soap  holding  a  certain  amount 
of  water  plus  the  glycerin  split  off  in  the  process  of  the  conversion 
of  the  fat  to  soap. 

It  is  a  matter  of  practical  experience  that  while  the  process 
of  soap  manufacture  in  the  cold  is  the  simplest,  the  results  thus 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    171 

obtained  are  not  always  so  satisfactory  as  when  the  process  is 
carried  out  at  a  higher  temperature.  It  is  also  a  matter  of  empiric 
knowledge  that  certain  fats  readily  yield  satisfactory  soaps  when 
used  in  the  cold  while  others,  it  might  almost  be  said,  never  do 
so.  The  extremes  are  represented,  on  the  one  hand,  by  the  use 
of  such  a  fat  as  castor  oil,  cottonseed  oil  or  even  palm  kernel  oil; 
on  the  other  hand,  by  the  use  of  hydrogenated  cottonseed  oil, 
stearin  or  Japan  wax. 

What  happens  becomes  intelligible  when  the  qualities  and 
quantities  of  the  fatty  acids  found  in  these  fats  and  oils  are  com- 
pared with  the  physico-chemical  and  colloid  properties  of  soaps 
which  are  produced  from  the  different  fatty  acids  as  illustrated 
in  Figs.  1  to  13. 1  Soaps  are  readily  made  by  the  cold  process  only 
from  such  fats  as  are  approximately  liquid  or  yield  fatty  acids 
which  are  liquid  at  the  temperature  at  which  the  soap  is  manufactured. 
In  the  older  schemes  of  soap  manufacture  this  process  was  regularly 
employed  with  such  oils  as  olive,  cocoanut  and  cottonseed.  Partly 
because  larger  and  larger  quantities  of  these  materials  are  now 
used  for  food,  and  partly  because  the  soaps  from  these  materials 
are  relatively  soft  and  "  wash  away "  easily  (and  for  toilet 
purposes,  for  example,  a  somewhat  firmer  product  is  desired) 
the  original  oils  have,  with  time,  had  admixed  with  them  larger 
and  larger  fractions  of  fats  with  higher  melting  points.  As  this 
has  happened  the  difficulty  of  making  the  soap  by  the  "  cold  " 
process  has  increased,  for  the  fats  rich  in  palmitic  acid,  stearic 
acid,  etc.,  cannot  be  thus  saponified.  At  higher  temperatures 
it  is,  of  course,  an  easy  matter.  Since  saponification  represents 
an  exothermic  reaction,  considerable  heat  is  produced  which 
warms  the  soap  mixture.  For  this  reason  fatty  acids  melting 
at  temperatures  considerably  above  that  of  the  surrounding 
medium  can  still  be  saponified  in  the  "  cold."  The  higher  (solid) 
fatty  acids  also  saponify  more  slowly  than  do  the  lower  ones, 
whence  the  common  practice  of  allowing  the  necessary  fat-alkali 
reaction  mixtures,  when  soap  is  produced  by  the  "  cold  "  process, 
to  stand  several  days,  while,  to  conserve  the  liberated  heat,  the 
vats  or  frames  are  protected  with  mattresses. 

The  now  almost  universally  employed  "  hot  "  process  of  soap 
manufacture  may  be  dismissed  with  the  remark  that  at  the  higher 
temperature  employed  all  the  oils  and  fats  used  (or,  in  the  TWITCH- 
1  See  pages  10  to  29. 


172 


SOAPS  AND  PROTEINS 


ELL  process,  the  fatty  acids  derived  from  them)  are  liquid 
and  that  their  saponification  in  consequence  occurs  quickly  and 
satisfactorily.  Since  only  a  few  hours  are  necessary  for  complete 
saponification  by  the  hot  process,  this  is  preferred  by  the  manu- 
facturer to  the  cold  process  which 
may  require  several  days  during 
which  his  vats,  frames  and  machines 
are  kept  employed  in  the  manufac- 
ture of  a  single  batch  of  soap. 

What  has  been  written  above  may 
be  readily  illustrated  in  laboratory 
experiments  which  follow  the  prac- 
tices of  the  soap  chemist.  In  Fig. 
93  are  shown  three  beakers  all  con- 
taining the  same  mixtures  of  cotton- 
seed oil  and  sodium  hydroxid,  the 
amounts  having  been  so  chosen  as 
^  to  yield  a  theoretically  neutral  soap. 
^  In  the  first  beaker  on  the  left  and 
in  the  middle  beaker,  the  sodium 
£  hydroxid  solution  has  been  poured 
in  a  single  "  charge  "  into  the  oil, 
the  former  having  been  left  without 
stirring,  the  latter  having  been  stirred 
immediately  until  the  mixture  showed 
signs  of  stiffening.  In  the  beaker  on 
the  right,  the  sodium  hydroxid  was 
added  in  three  separate  "charges" 
(as  is  the  practice  in  manufacturing) , 
proper  stirring  following  each  new 
addition  of  alkali.  The  photograph 
was  taken  the  following  day.  It 
will  be  observed  that  without  stirring 
only  a  thin  soap  layer  (very  dry) 

forms  between  the  oil  and  the  watery  alkali  and  saponification 
seems  to  come  to  a  stop;  that  when  added  at  once  with 
satisfactory  stirring  a  fine  clear  soap  is  obtained;  that  when 
added  in  three  fractions  a  good  soap  but  of  less  perfect  appear; mre 
results.  We  shall  return  to  these  findings  later,  but  it  is  evident, 
at  this  time  that  from  a  low  melting  point  fat  a  satisfactory  soap 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE     173 


may  be  obtained  by  the  cold  process  if  only  the  requisite  amount 
of  sodium  hydroxid  is  added  quickly 
and   at    once,  the   mixture  is  stirred 
until  it  shows  definite  signs  of  stiffen- 
ing and  is  then  left  to  itself. 

Fig.  94  shows  that  when  the  cot- 
tonseed oil  is  hydrogenated,  when,  in 
other  words,  its  oleic  acid  is  converted 
into  stearic  (and  similarly,  perhaps, 
certain  other  unsaturated  acids  into 
saturated  ones)  the  "  cold "  process 
no  longer  suffices  to  make  soap.  The 
appearance  of  the  first  beaker  on  the 
left  in  Fig.  94  must  be  compared  with 
that  of  the  middle  beaker  in  Fig.  93. 
While  no  soap  seems  to  have  been 
produced  in  the  cold,  saponification 
of  the  hydrogenated  fat  is  satisfactory 
as  soon  as  the  reaction  mixture  is 
heated  for  a  time,  as  evidenced  in  the 
second  beaker  from  the  left  of  Fig. 
94.  The  same  general  truths  are 
brought  out  in  the  three  right-hand 
beakers  of  Fig.  94  in  which,  to  mimic 
accepted  technical  procedures  more 
perfectly,  a  sodium  hydroxid  of  lower 
concentration  and  a  reaction  mixture 
containing  a  larger  total  of  water  were 
used  to  accomplish  saponification  of 
the  hydrogenated  cottonseed  oil.  The 
middle  beaker  of  the  whole  series 
shows  that  saponification  is  again  im- 
possible in  the  "  cold."  A  partial  result 
is  obtained  if  the  beaker  is  heated  to 
above  the  liquefaction  point  of  the  fat 
and  the  mixture  is  stirred;  but  to  get 
complete  saponification  the  reaction 

mixture  must  be   kept   some  time  at . 1 

this  high  temperature  as  shown  by  the 

satisfactory  result  in  the  beaker  on  the  extreme  right  of  the  series. 


174  SOAPS  AND  PROTEINS 

Having  observed  how  the  type  of  oil  or  fat  employed  determines 
from  a  chemical  point  of  view  whether  a  cold  or  hot  process  of 
manufacture  will  yield  best  results,  we  need  to  review  the  whole 
process  once  more  from  the  point  of  view  of  the  changes  which 
are  incident  to  the  mere  mixing  of  any  fat  or  oil  with  an  alkali. 
The  empiric  instructions  covering  the  process  are  again  many.1 
In  the  case  of  certain  "  oils  "  a  stronger  alkali  may  be  used  than 
when  the  more  solid  "  fats  "  are  employed;  or  in  the  case  of  the 
former  all  the  alkali  may  be  added  more  quickly  or  in  one  charge 
while  in  the  latter  several  successive  and  smaller  charges  must 
be  used.  The  soap  maker  has  here  again  learned  from  practical 
experience  what  may  be  done  with  any  individual  oil  or  fat,  or 
what  may  be  accomplished  by  mixing  or  blending  such.  What 
do  these  things  mean? 

The  older  soap  chemists  recognized  that,  in  their  "  cold  " 
process  of  manufacture,  emulsification  of  the  fat  played  an 
important  role;  what  happened  in  the  hot  process  was  not  so 
clear. 

5.  The  Mixing  of  Fat  with  Alkali.    Initial  Emulsification 

J.  LEIMDORFER  2  has  correctly  said  that  the  colloid-chemistry 
of  soaps  begins  with  the  commencement  of  their  manufacture 
and  in  defense  of  this  remark  has  emphasized  anew  the  signifi- 
cance of  emulsification  in  the  cold  method  of  soap  manufacture. 
LEIMDORFER  points  out  that  when  any  fat  is  mixed  with  caustic 
soda  solution  the  two  are  emulsified  in  each  other  and  that  in 
the  "  gum  "  or  jelly  which  results,  the  process  of  saponification 
then  proceeds  to  an  end.  According  to  LEIMDORFER  the  soap 
formed  "  adsorbs  "  the  alkali  and  the  fat,  the  further  reaction 
between  these  materials  occurring  in  the  soap  gel  itself,  as  it  were. 
We  shall  have  occasion  to  touch  upon  the  "  adsorption  "  pli.ix- 
of  this  explanation  later.  At  this  point  we  wish  merely  to  con- 
sider in  somewhat  greater  detail  the  initial  process  of  emulsi- 
fication. 

It  is  held  by  various  authors  that  the  occurrence  or  non- 
occurrence  of  this  initial  process  of  emulsification  makes  possible 

1  As  an  illustration  of  the  technical  literature  extant  see,  for  example, 
ALEXANDER  WATT:  The  Art  of  Soap  Making,  Ninth  Imp.,  London  (11)  I  s 

2  J.  LEIMDORFER:  Technologic  der  Seife,  5,  Dresden  (1911). 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    175 

or  impossible  soap  formation  by  the  "  cold "  process.  This 
conclusion  has  been  drawn  from  the  fact  that  the  fats  which  do 
not  emulsify  readily  in  the  cold  also  fail  to  saponify  easily.  While 
proper  previous  emulsification  does  accelerate  saponification,  the 
real  difficulty  is  resident  in  the  nature  of  the  fatty  acids  present 
in  the  more  solid  fats — the  higher  (solid)  fatty  glycerids  being 
split  with  greater  difficulty  and  the  resulting  fatty  acids  combin- 
ing more  slowly  with  alkali  at  low  temperatures  than  do  the 
more  liquid  oils  with  their  lower  and  more  nearly  liquid  fatty 
acids. 

For  the  production  of  an  emulsion,  whether  soap  be  made 
by  the  cold  or  the  hot  process  and  whether  from  neutral  fat  or 
the  free  fatty  acids,  it  is  necessary  to  hold  distinctly  in  mind  the 
mere  making  of  the  emulsion  and  its  subsequent  stabilization. 
Aid  is  rendered  the  first  process  by  the  mechanical  agitation 
incident  to  the  mere  mixing  of  the  soap-kettle  constituents. 
Usually,  also,  a  new  batch  of  soap  is  started  by  running  the  new 
mass  of  fat  or  oil  to  be  saponified  into  a  kettle  containing  the 
soap  remnants  left  from  a  previous  run.  But  even  if  a  caustic 
alkali  is  run  at  once  into  a  cold  or  a  hot  fat,  soap  formation  begins 
very  quickly,  for  rarely  are  these  substances  free  from  a  certain 
amount  of  free  fatty  acid.  As  previously  emphasized,  it  is  not 
possible  to  emulsify  fat  in  pure  water.  In  soap  manufacture, 
therefore,  the  fat  is  not  emulsified  in  water  but,  as  is  necessary  in 
all  such  instances,  in  a  liquid  hydrated  colloid.  Hence  the  use- 
fulness of  beginning  with  a  soap  stock,  the  greater  ease  of  emulsi- 
fication if  the  fat  used  is  liquid  at  the  temperature  employed  and 
contains  free  fatty  acid,  and  the  exceeding  simplicity  of  the  whole 
process  if  all  the  soap  is  made  from  free  fatty  acid  (by  the  TWITCH- 
ELL  process).  The  first  portion  of  hydrated  colloid '  found 
or  produced  in  the  soap  kettle  then  permits  the  fats  or  fatty  acids 
added  subsequently  to  be  properly  and  permanently  emulsified 
in  them. 

The  ease  with  which  such  emulsification  is  obtained  is  in 
its  turn  resident  in  the  physical  qualities  of  the  fat  itself.  It 
is  obvious  that  emulsification  can  be  obtained  more  easily  in  the 
case  of  a  low  melting  point  fat,  like  the  liquid  oils,  than  in  that 
of  the  more  solid  fats,  like  tallow,  stearin  or  Japan  wax.  Emul- 
sions are  subdivisions  of  a  liquid  in  a  liquid.  To  get  the  more 
solid  fats  into  this  state  an  increase  in  temperature  is  therefore 


176 


SOAPS  AND  PROTEINS 


demanded.     It  is  for  this  reason  that  the  high  melting  point 
fats,  which  are  least  likely  to  yield  satisfactory  emulsions  (and 


FIGURE 


which  saponify  badly)   at  low  temperatures,  are  best  used  at 
higher  temperatures. 

Another  factor  in  this  matter  of  emulsification  is  found  in 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    177 

the  properties  of  the  soap  formed  to  act  as  the  colloid  hydrate 
for  the  emulsification  of  the  fat.    For  proper  emulsification  there 


95. 


is  necessary  not  only  an  optimum  concentration  of  the  soap 
used,  but  also  a  suitable  kind  of  soap. 

For  soap  manufacture  by  the  cold  process  the  soaps  of  the 


178  SOAPS  AND  PROTEINS 

lower  fatty  acids  of  the  acetic  series  and  the  oleates,  linolates, 
etc.,  act  best  as  emulsifying  agents,  for  these  yield  liquid  hydrated 
colloids  at  the  low  temperatures  prevailing  in  the  reaction  mixture. 
When,  however,  soap  manufacture  is  carried  out  at  a  higher 
temperature  it  is  obvious  that  soaps  of  the  higher  fatty  acids 
will  act  better,  for  at  these  higher  temperatures  the  soaps  of  the 
lower  fatty  acids  will  have  "  gone  into  true  solution,"  thus  losing 
their  hydrophilic  character.  While  the  soaps  of  the  higher  fatty 
acids  are  solid  in  the  cold  process  and  of  little  use  for  emulsi- 
fication  purposes,  they  become  liquid  hydrated  colloids  at  the 
higher  temperatures  and  stabilize  any  emulsion  that  may  be 
formed. 

It  is  of  interest  to  examine  iriicroscopically  the  changes  inci- 
dent to  this  emulsification  process.  Fig.  95  shows  the  successive 
changes  observable  when  soap  is  made  by  the  cold  process  from 
cottonseed  oil  and  caustic  soda.  After  the  two  materials  have 
been  stirred  into  each  other  as  previously  described  for  the  middle 
beaker  of  Fig.  93,  a  soap  is  rapidly  formed  (since  cottonseed  oil 
usually  contains  some  free  fatty  acid)  in  which  the  unused  portions 
qf  oil  then  become  dispersed  as  shown  in  photomicrograph  A 
of  Fig.  95.  If  a  drop  of  this  mixture  is  watched  under  the  micro- 
scope for  a  little  time,  the  oil  droplets  are  found  to  diminish  in 
size  while  becoming  surrounded  with  an  increasingly  thicker  halo 
of  hydrated  soap.  This  is  shown  in  B.  The  halo  grows  in  thick- 
ness until  the  whole  alkali-fat  mixture  sets  into  a  firm  jelly,  the 
appearance  at  this  stage  being  represented  by  C.  In  the  course 
of  a  number  of  hours  or  several  days  the  whole  reaction  mixture 
comes  to  chemical  equilibrium,  when  it  presents  the  more  or 
less  uniform  appearance  of  D.  This  final  picture  represents  a 
hydrated  mixed  soap  in  which  the  soaps  of  the  higher  fatty  acids 
tend  to  crystallize  within  the  soaps  possessed  of  lower  melting 
points. 

6.  Concentration  of  Alkali  and  Method  of  Adding  it  for 
Saponification 

We  need  now  to  go  back  over  the  course  of  soap  making  a 
third  time  in  order  to  analyze  for  a  moment  some  of  the  practical 
facts  utilized  in  determining  the  method  and  the  concentration 
at  which  an  alkali  is  added  to  different  fats  and  oils  for  their 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    179 

saponification.  It  may  be  stated  as  generally  true  that  alkali 
may  be  added  in  high  concentration  or  in  a  single  charge  of  the 
theoretically  necessary  amount  onfy  to  such  liquid  fats  as  cotton- 
seed oil,  castor  oil,  linseed  oil,  cocoanut  oil  or  palm  kernel  oil. 
When  tallow,  stearin  or  Japan  wax  soap  is  to  be  made,  the  alkali 
must  be  added  in  several  smaller  charges  and  the  concentration 
of  alkali  in  the  individual  charges  must  be  lower.  To  give  specific 
examples  the  following  may  be  cited.  Linseed  oil  may  be  saponi- 
fied by  adding  to  it  at  once  the  requisite  amount  of  sodium  hy- 
droxid  at  24°  to  28°  Baume  (17.6  to  21.4  percent);  cocoanut  oil 
will  tolerate  a  first  charge  at  16°  to  20°  Baume  (10.9  to  14.3  per- 
cent). Against  these  figures  tallow  must  be  treated  with  a  first 
fractional  charge  at  11°  Baume  (7.3  percent)  succeeded  by  a 
second  at  12°  to  15°  Baume  (8.0  to  10.0  percent).  Even  the 
final  charge  may  not  safely  exceed  20°  Baume  (14.3  percent). 
What  is  the  explanation  for  these  empirically  well  known  facts? 
It  is  not  a  matter  merely  of  the  readier  saponification  of  the  lower 
melting  point  fatty  acids  found  in  the  oils  or  of  the  greater  tendency 
of  the  higher  fatty  acid  soaps  to  hydrolyze.  Were  this  the  case, 
then  the  higher  concentrations  of  alkali  should  act  best  upon 
the  higher  melting  point  fats,  while  just  the  opposite  is  the  case. 
It  is  the  greater  sensitiveness  of  the  soaps  of  the  higher  fatty  acids  to 
salting-out  effects  (of  the  sodium  hydroxid  in  this  case)  which 
explains  these  empiric  findings.  The  soaps  of  castor  oil,  linseed 
oil  and  cocoanut  oil  can  scarcely  be  salted  out  by  sodium  hydroxid 
at  any  concentration,  while  the  sodium  palmitate,  stearate, 
arachidate,  etc.,  formed  from  tallow,  Japan  wax,  etc.*,  come  out 
in  very  low  concentrations  of  alkali.1  The  use  of  larger  volumes 
of  sodium  hydroxid  containing  lower  concentrations  of  the  alkali 
in  the  production  of  the  tallow  soaps  means  that  the  soap  as 
formed  has  more  solvent  present  in  which  "  to  dissolve  "  while 
the  concentration  of  alkali  present  in  this  solvent  is  not  sufficient 
to  salt  out  the  soap.  The  alkali  added  in  a  first  charge  is  lost 
from  the  system  as  it  combines  with  the  fat  to  make  soap,  in 
consequence  of  which  the  second  charge  may  be  of  higher  concen- 
tration for  this  is  quickly  diluted  on  entering  the  soap  kettle  by 
the  volume  of  water  carried  in  with  the  first  charge.  With  the 
second  charge  of  alkali  used  up  in  saponification,  the  third  charge 
is  quickly  diluted  with  the  water  left  from  the  previous  charges  to 
1  See  pages  116  to  120. 


180  SOAPS  AND  PROTEINS 

a  concentration  which  will  not  in  its  turn  salt  out  the  soap,  for 
it  is  at  all  times  the  concentration  and  not  the  amount  of  alkali 
(or  other  salt)  in  the  entire  soap/water  system  which  determines 
its  salting-out  effects. 

Given  the  qualitative  composition  of  a  fat,  the  upper  limit  of  the 
concentration  of  any  hydroxid  which  may  be  used  for  its  saponi- 
fication  is  determined  by  the  concentration  at  which  the  soap  of  the 
highest  fatty  acid  found  in  that  fat  is  salted  out  at  the  temperature 
prevailing  in  the  soap  vat. 

7.  The  Changes  in  Soap  Systems  Consequent  upon  Cooling 

The  first  change  to  be  discussed  as  the  temperature  of  a  boiling 
soap/water  system  is  lowered  (whether  it  contains  glycerin  or 
not)  is  that  of  its  tendency  to  change  from  what  at  the  higher 
temperature  was  a  solution  of  soap-in-water  to  that  which  at  the 
lower  is  one  of  water-in-soap.  The  apparently  contradictory 
findings  and  views  which  different  authors  have  recited  covering 
the  nature  of  the  changes  observed  may  all  be  harmonized  when 
these  changes  from  one  system  to  the  other  (including  the  pos- 
sible intermediates  of  an  "  emulsion  "  of  hydrated  soap  in  soap 
water  followed  by  one  of  soap  water  in  hydrated  soap)  are  kept 
in  mind. 

Beginning  with  the  days  of  CHEVREUL,  the  soaps  were  held  to 
be  salts  of  the  fatty  acids  containing  a  definite  amount  of  water 
of  crystallization  which  on  solution  in  water  yielded  "  solutions  " 
like  all  other  salts.  Many  physical  chemists  held  to  this  view 
into  the  nineties  of  the  last  century,  for  pure  and  mixed  soaps  in 
dilute  solution  showed  an  osmotic  pressure,  an  electrical  conduc- 
tivity, a  depression  of  the  freezing  point  or  elevation  of  the  boiling 
point  quite  like  "  normal  "  electrolytes.  (JAMES  W.  McBAiN,  M. 
TAYLOR,  C.  C.  V.  CORNISH  and  R.  C.  BOWDEN/  McBAiN  and 
TAYLOR2).  Following 'the  studies  of  F.  KRAFFT  and  H.  WiGLOw,3 

1  JAMES  W.  McBAiN,  M.  TAYLOR,  C.  C.  V.  CORNISH  and  R.  C.  BOWDEN: 
Berich.  d.  deut.  chem.  Gesellsch.,    43,  321  (1910);    Jour.  Chem.  Soc.,  101, 
2041  (1913). 

2  McBAiN  and    TAYLOR:    Zeitschr.    f.  physik.  Chem.,   76,   179    (1911); 
since   this    time,  however,  these   authors    have    modified    their  views;   see 
Jour.  Am.  Chem.  Soc.,  42,  426  (1920). 

»  F.  KRAFFT  and  H.  WIGLOW:  Berich.  d.  deut.  chem.  Gesellsch.,  28,  2573 
(1895), 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    181 

A.  SMiTS,1  F.  GOLDSCHMIDT  and  L.  WEissMANN,2  these  views 
received  modification.  KRAFFT  and  WIGLOW  observed  that  when 
the  soaps  of  the  higher  fatty  acids  were  studied  at  low  tempera- 
tures these  commonly  did  not  lower  the  freezing  point  in  the  cal- 
culated amount;  and  GOLDSCHMIDT  found  that  the  electrical  con- 
ductivity was  not  as  high  as  theory  demanded.  The  same  soaps 
when  studied  at  sufficiently  high  temperatures  did,  however, 
show  the  behavior  of  normal  electrolytes.  Obviously  the  earlier 
observers  and  those  working  at  high  temperatures  dealt  with  what 
were  essentially  true  solutions  of  soaps  in  water;  the  latter  stu- 
dents of  the  problem,  working  at  lower  temperatures  and  with 
higher  fatty  acid  soaps,  dealt  with  mixed  systems.  The  former 
worked  in  the  region  A  of  Figs.  48  and  49;  the  latter  anywhere  below 
this  but  still  in  regions  in  which  were  present  solutions  of  soap-in- 
water  admixed  with  solutions  of  water-in-soap.  What  characteristics 
of  a  "  true  "  solution  their  mixtures  still  showed  were  dependent 
upon  the  presence  of  the  former;  the  characteristics  at  variance  with 
those  anticipated,  in  other  words,  the  "  colloid  "  properties  of  the 
systems  were  dependent  upon  the  latter. 

8.  The  Salting-Out  of  Mixed  Soaps 

The  sal  ting -out  of  mixed  soaps  has  been  made  the  object  of 
special  study  by  MERKLEN  3  and  LEiMDORFER.4  Both  give  excel- 
lent analyses  of  the  content  of  soap,  water  and  dissolved  sub- 
stances (like  alkali  and  salts)  present  in  the  two  main  phases,  the 
"  lye  "  and  the  "  curd  "  or  "  settled  "  soap,  which  may  be  ob- 
tained after  complete  or  partial  salting-out. 

The  observations  detailed  in  the  previous  pages  on  the  salting- 
out  of  the  different  soaps  help  us  to  explain,  we  think,  in  simpler 
fashion  than  is  generally  the  case  the  series  of  changes  observed 
in  the  contents  of  the  soap  kettle  when  salted  and  cooled.  In  the 
ordinary  salting-out  process  common  sodium  chlorid  is  shoveled 
into  the  boiling  soap  kettle  in  dry  form.  Assuming  that  it  goes 
into  solution  at  once,  it  is  obvious  that  there  follows  a  progressive 
increase  in  the  concentration  of  the  salt  in  a  soap/water  system. 

1  A.  SMITS:  Zeitschr.  f.  physik.  Chem.,  45,  608  (1903). 

2  F.  GOLDSCHMIDT  and  L.  WEISSMANN:   Zeitschr.  f.  Electrochem.,  18,  380 
(1912). 

3  FRANCOIS  MERKLEN:  Die  Kernseifen,  trans,  by  FRANZ  GOLDSCHMIDT. 
Halle  a/S  (1907). 

4  J.  LEIMDORFER:  Technologic  der  Seife,  Dresden  (1911). 


182  SOAPS  AND  PROTEINS 

While  it  is  ordinarily  thought  that  all  the  soaps  present  in  the  mix- 
ture of  soaps  in  the  soap  kettle  begin  to  separate  out  as  soon  as  a 
sufficient  concentration  of  the  salt  has  been  obtained,  the  quan- 
titative studies  previously  detailed  show  that  this  is  by  no  means 
the  case.  A  concentration  of  salt  which  will  salt  out  the  soaps 
of  the  higher  fatty  acids  of  the  acetic  series  will  obviously  be 
reached  sooner  than  one  which .  will  salt  out  the  lower  soaps. 
While,  for  instance,  a  sodium  stearate  is  salted  out  in  the  cold 
by  a  5°  Baume  sodium  chlorid  solution,  sodium  laurate  requires 
a  17°  Baume  salt  water  (C.  STIEPEL  l).  The  general  truth  of  this 
law  finds  expression  in  the  fact  that  after  apparent  total  separation 
of  the  mixed  soaps  as  a  curd  from  the  spent  lye,  the  latter  still 
contains  some  soap.  But  the  contained  soaps  are  essentially 
those  of  the  lower  fatty  acids.  The  curd  per  contra  is  relatively 
poor  in  these. 

During  the  process  of  salting-out,  a  soap  mixture  frequently 
"  gums,"  "  goes  stringy  "  and  tends  to  boil  over,  a  situation 
which  the  practical  soap  maker  has  learned  to  meet  by  rapidly 
shoveling  in  more  salt.  The  explanation  of  what  happens  is 
found  in  the  experiments  on  the  salting-out  of  soaps.  Before 
complete  salting-out  is  obtained  the  previously  liquid  soap  mix- 
tures tend  to  gel  because  of  the  emulsification  within  them  of 
salt-water.  Through  the  addition  of  more  salt,  however,  the 
amount  of  this  salt-water  phase  is  increased  and  as  this  happens, 
change  in  type  of  emulsion  occurs — the  hydrated  soap  now  becom- 
ing dispersed  within  the  salt-water  as  the  external  phase, — and 
the  viscosity  of  the  kettle  contents  falls. 

It  is  the  common  practice  in  the  salting-out  of  soaps  to  add 
dry  salt  to  the  soap  kettle.  This  represents  economy,  of  course, 
from  the  point  of  view  of  the  amount  of  salt  needed,  for  it  is  the 
concentration  of  the  salt  in  the  total  volume  of  water  present 
which  determines  when  the  mixed  soaps  will  "  come  out  of  solu- 
tion." Solution  of  the  crystals  of  salt  in  the  soap  kettle,  how- 
ever, takes  time  and  even  the  shoveling  in  of  more  salt  into  the 
soap  kettle  does  not  at  once  increase  the  concentration  of  dis- 
solved salt.  The  use  of  a  proper  brine  under  such  circumstances 
would  work  better  and  more  rapidly  in  bringing  the  soap  kettle 
contents  to  the  safe  side  of  the  gelation  point  of  the  mixture. 

1  C.  STIEPEL:  Fette,  Oele  und  Wachse,  usw.,  112,  Leipzig  (1911).  See  also 
page  116. 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    183 

There  needs  also  to  be  explained  the  differences  incident  to  the 
salting-out  of  soap  at  a  high  temperature  and  at  a  lower  one. 
Soap  being  more  soluble  in  water  at  a  higher  temperature,  a  higher 
absolute  concentration  of  salt  is  required  to  salt  it  out  at  such 
than  at  a  lower  one.  The  slow  reversal  in  the  system  from  one  of 
soap-in- water  to  one  of  water-in-soap  with  lowering  of  tempera- 
ture needs  also  to  be  kept  in  mind.  This  explains  the  slow  gela- 
tion commonly  observed  in  the  "  lye  "  after  the  whole  soap-water- 
salt  mixture  has  been  allowed  to  stand  for  a  number  of  hours. 
The  soaps  of  the  lower  fatty  acids  which  are  still  soluble  in  water 
at  the  higher  temperatures,  even  when  sodium  chlorid  or  other 
salt  has  been  added  to  the  point  where  most  of  the  soaps  are  salted 
out,  slowly  come  out  of  solution,  become  hydrated,  and  if  enough 
of  such  are  present,  the  lye  itself  gels.1 

9.  The  Finishing  of  Soap 

Soap  may  be  "  finished  "  for  market  purposes  in  the  soap  kettle 
itself.  More  commonly,  however,  the  "  curd  "  obtained  after 
complete  salting-out  of  a  soap  is  reheated,  redissolved  in  more  or 
less  water  and  salted  out  more  or  less  completely  a  second  time 
by  again  being  treated  with  sodium  chlorid  of  different  concen- 
trations. 

Depending,  on  the  one  hand,  upon  the  kind  of  fatty  acids  and 
their  quantitative  relation  to  each  other  in  a  given  mixture  (fac- 
tors commonly  ignored),  upon  the  other,  on  the  amount  of  sodium 
chlorid  added,  there  may  be  obtained  (1)  a  grained  or  curd  soap, 
(2)  a  settled  soap,  (3)  a  half-settled  soap  or  (4)  a  soft  soap. 

1  This  is  the  system  obtained  in  making  a  "settled"  soap  (the  "Kernseife 
auf  Leimniederschlag "  of  the  Germans)  and  that  upon  which  MERKLEN 
made  most  of  his  observations.  He  considers  the  gelatinous  lye  "a  solution 
of  soaps  in  an  alkaline  lye  containing  salts;"  the  soap  curd  also  "a  solution 
of  soaps  in  an  alkaline  lye  containing  salts"  and  holds  the  two  to  represent 
"phases"  in  equilibrium  with  each  other  (FRANCOIS  MERKLEN:  Die  Kern- 
seifen  13,  Hallea  /S  (1907)).  As  obvious  from  the  above,  the  "curd"  phase  isa 
highly  concentrated  one  of  hydrated  (higher  fatty  acid)  soap  containing  some 
salt-water  emulsified  in  it;  the  "lye"  phase  (when  gelatinous)  also  one  of 
hydrated  (lower  fatty  acid)  soap  of  lower  concentration  and  containing  a 
high  percentage  of  salt-water  emulsified  within  it.  See  the  succeeding  section. 


184  SOAPS  AND  PROTEINS 


§1 

The  grained  or  curd  soap  is  obtained  whenever  enough  sodium 
chlorid  is  added  for  complete  salting-out  of  the  soap.  Under  such 
circumstances  the  vat  contents  separate  into  two  distinct  phases; 
an  upper  consisting  in  essence  of  pure  soap  containing  very  little 
water  and  very  little  sodium  chlorid,  and  a  lower,  in  essence  only  a 
strong  sodium  chlorid  solution  containing  practically  no  soap. 

For  the  production  of  a  settled  soap  a  lower  concentration  of 
sodium  chlorid  is  used.  Under  such  circumstances  separation 
into  two  phases  also  occurs.  The  upper  is  again  essentially  a 
curd  soap  but  it  is  less  dry  this  time.  Because  of  the  larger 
proportion  of  water  the  soap  is  smoother  and  of  a  more  homogene- 
ous structure.  It  also  contains  a  larger  fraction  of  salt.  The 
lower  phase  is  still  in  essence  a  "  salt  solution  "  but  because  of 
the  less  perfect  salting-out  of  the  soap  (especially  of  those  soaps 
least  sensitive  to  salt  action)  this  phase  still  contains  so  high  a 
fraction  of  "  dissolved  "  soap  that  on  cooling  it  jellies.  The  soap 
system  as  a  whole  represents  what  the  Germans  call  "  Kernseife 
auf  Leimniederschlag  "  and  it  is  this  system  which  FRANCOIS 
MERKLEN  1  has  studied  in  detail  and  to  which  he  has  applied  the 
phase  rule.  We  question  whether  the  true  nature  of  the  two  phases 
has  been  correctly  understood  by  this  author, — scarcely  a  matter 
of  surprise  when  it  is  remembered  that  he  worked  throughout 
with  mixed  soaps.  In  our  judgment,  the  series  of  changes  ob- 
served and  the  nature  of  the  two  phases  finally  obtained  seems 
to  be  as  follows.  The  concentration  of  sodium  chlorid  added  to 
the  original  soap  solution  is  such  as  will  salt  out  the  various  soaps 
unequally  well  and  only  partially.  The  soaps  most  sensitive  to 
the  presence  of  salt  will  obviously  tend  to  come  out  first,  whence 
the  upper  phase  or  "  curd  "  (rich  in  soaps  of  the  higher  members 
of  the  acetic  series,  the  oleates,  linolates,  etc.,  and  relatively  poor 
in  water)  caught  in  the  meshes  of  which  is  a  certain  amount  of 
salt  water.  The  latter  is  responsible  for  the  higher  fraction  of 
salt  found  in  settled  soaps  when  compared  with  pure  curd  soaps. 
Some  soaps,  especially  those  produced  from  the  lower  members  of 
the  acetic  series,  remain  in  solution  in  the  lower  or  salt  water 
phase  but  with  time  these,  too,  fall  out  of  solution  and  become 

1  FRANCOIS  MERKLEN:  IStude  surla  constitution  des  savons  du  commerce, 
Marseilles  (1906). 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    185 

hydrated,  whence  the  late  jellying  of  the  lower  of  the  two  phases 
in  the  vat.  After  such  jellying  has  occurred,  the  lower  phase  is 
qualitatively  similar  to  the  upper  phase  but  different  in  quan- 
titative composition.  The  lower  phase,  too,  is  an  emulsion  of 
salt  water  in  hydrated  soap,  but  viewed  as  a  whole  this  system 
is  poorer  in  soap,  and  richer  in  water  and  sodium  chlorid. 

To  produce  half-settled  soap,  still  less  sodium  chlorid  is  used  in 
the  finishing  of  an  originally  curded  soap  or,  as  commonly  prac- 
ticed, not  enough  salt  is  added  to  the  hot  contents  of  the  soap 
kettle  to  get  any  salting-out.  On  cooling,  the  kettle  contents  sim- 
ply become  fairly  solid.  Separation  into  two  distinct  phases 
does  not  occur,  the  contents  of  the  kettle  or  soap  vat  simply 
changing  to  a  soap  which  in  essence  is  an  emulsion  of  salt  water  in 
a  relatively  highly  hydrated  soap. 

If  the  attempt  is  made  to  increase  still  further  the  water- 
holding  capacity  of  a  soap,  a  mixture  is  finally  obtained  which  is 
no  longer  definitely  solid.  We  then  have  a  so-called  soft  soap. 

The  above  paragraphs  have  described  the  finishing  process  in 
soap  manufacture  as  carried  out  with  sodium  chlorid.  In  prac- 
tice, however,  other  materials  having  an  action  similar  to  that  of 
sodium  chlorid  may  be,  and  are,  used  to  accomplish  similar 
ends.  Instead  of  being  "  filled  "  with  sodium  chlorid  solution, 
soaps  may  be  filled  with  ingredients  more  useful  in  washing,  like 
sodium  carbonate,  borax  or  water-glass.1  Under  such  circum- 
stances there  are  also  obtained  as  final  products,  emulsions  or 
"  solutions  "  of  these  various  materials  in  hydrated  soap. 

§2 

The  inequality  in  distribution  of  such  a  dissolved  substance 
as  sodium  chlorid,  alkali  or  sodium  carbonate  between  the 
two  phases  commonly  produced  in  a  soap  vat  (the  upper  soap- 
rich  phase  and  the  lower  soap-poor  phase)  has  often  been  inter- 
preted in  the  terms  of  "  adsorption."  There  is  still  much  debate 
about  the  nature  of  adsorption,  though  it  is  generally  assumed 
that  the  union  between  adsorbent  and  adsorbed  material  is  of  a 
physical  character  and  that  it  follows  the  adsorption  law,  which 
states,  in  brief,  that  an  adsorbent  will  take  up  relatively  more 
of  a  dissolved  substance  from  a  dilute  solution  than  from  a  more 
1  See  the  succeeding  section,  page  192. 


186  SOAPS  AND  PROTEINS 

concentrated  one.  Without  pointing  out  that  none  of  the  authors 
who  have  used  the  concepts  of  adsorption  for  the  elucidation  of 
various  problems  in  soap-making  have  ever  supported  their  con- 
tentions with  any  figures,  it  is  obvious,  if  the  views  expressed 
above  are  correct,  that  what  they  have  taken  as  evidences  of  "  ad- 
sorption "  between  various  so-called  "  dissolved  "  substances  and  the 
soaps  (alkali,  fat  and  soap  in  the  original  soap  kettle;  water,  salt 
and  soap  in  the  salting-out  process;  sodium  carbonate,  water- 
glass  and  soap  in  the  "  filling  "  process,  etc.)  can  all  be  more  easily 
understood  merely  as  the  expression  of  the  emulsification  of  one  type 
of  liquid  (like  fat  or  salt  solution)  in  a  second  (the  soaps  of  the 
various  fatty  acids  with  their  variable  hydration  capacities). 

§3 

In  the  finishing  of  soaps  (particularly  the  toilet  soaps)  for  the 
market,  there  is  often  added  glycerin  or  some  other  alcohol. 
Under  such  circumstances  the  product  is  more  likely  to  be  trans- 
parent. The  reasons  for  this  are  found  in  the  nature  of  the  col- 
loid-chemical system  soap/alcohol  as  compared  with  that  of  soap/ 
water.  The  former  is  uniformly  clearer  than  the  latter.  From 
certain  soap/alcohol  systems,  like  sodium  palmitate  with  benzyl 
alcohol,  finished  soaps  may  be  obtained  which  are  glasslike  in 
appearance. 

10.  Some  Physical  Constants  of  Market  Soaps 

§1 

Exclusive  of  admixture  with  non-saponifiable  materials,  exclu- 
sive of  the  effects  of  all  additions  in  the  way  of  excess  alkali,  salts 
or  fillers  and  exclusive  also  of  variation  in  type  of  solvent  (pres- 
ence or  absence  of  glycerin  or  other  alcohols)  a  correct  estimate  of 
what  will  be  the  physico-chemical  properties  of  any  soap  must 
evidently  depend  first,  upon  the  kind,  the  number  and  the  relative 
proportions  of  the  fatty  acids  found  in  the  original  fat  used  for 
saponification.  With  a  given  base  and  with  a  constant  solvent 
(water)  the  result  is  that  obtained  when  such  a  mixture  of  dif- 
ferent soaps  is  allowed  to  come  together  in  the  presence  of  a  lim- 
ited amount  of  water. 

The  ordinary  bar  of  pure  soap  is  therefore  essentially  only  a 
solid  "  solution  "  of  water  in  a  mixture  of  sodium  soaps.  Except 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE     187 

in  the  instance  of  soaps  designed  to  meet  special  purposes,  the 
stock  sodium  soap  contains  a  long  list  of  different  fatty  acids 
and  as  such  serves  to  meet  technologic  needs  under  the  largest 
number  of  ordinary  circumstances.  Usually,  in  the  manufacture 
of  such  soap  some  liquid  oil  or  fat  (like  cocoanut  oil)  has  had 
added  to  it  smaller  fractions  of  the  more  solid  fats  (like  stearin, 
tallow  or  Japan  wax).  The  result  is  a  set  of  some  eight  to  fifteen 
different  soaps  of  widely  varying  "  solubility  "  in  water  and  sen- 
sitiveness to  salt  action,  and  possessed  of  a  chain  of  fatty  acids  of 
progressively  different  melting  points. 

When  such  a  mixed  soap  is  completely  salted  out  from  its 
"  solvent  "  as  a  curd  soap  it  is  a  relatively  dry  affair,  the  yield 
from  100  parts  of  the  original  fat  being  only  about  150  parts  of 
finished  soap.  When  neutral  and  carefully  handled  this  is  the 
basis  of  most  of  the  common  toilet  soaps.  The  advantages  of 
such  a  material  for  all  ordinary  purposes  are  obvious.  The  soap  is 
free  from  any  excess  of  alkali  or  sodium  chlorid  and  the  series  of 
soaps  present  yields  a  satisfactory  (liquid)  hydrated  colloid  with 
water  at  any  of  the  ordinary  temperatures  at  which  it  may  be  used. 
Since,  moreover,  in  the  salting-out  process,  the  higher  acetic 
series  soaps  come  out  first  and  the  lower  ones  with  the  oleate  come 
out  later,  the  arrangement  of  the  different  soaps  within  the  solid 
bar  is  also  such  that  the  most  readily  "  soluble  "  soaps  become 
hydrated  and  dissolve  first,  thus  favoring  disintegration  of  the 
bar  for  the  production  of  the  hydrated  liquid  colloid  required 
for  washing. 

It  is  well  to  discuss  here  the  composition  and  nature  of  the 
so-called  hot  and  cold  water  soaps  and  the  marine  soaps.  A 
cold  water  soap  is  one  which  will  in  cold  water  yield  the  (liquid) 
hydrated  colloid  necessary  for  washing.  Obviously  only  soaps 
rich  in  the  lower  fatty  acids  of  the  acetic  series  will  do  this,  and 
hence  the  use  of  pure  cocoanut  oil  for  the  production  of  such  a 
soap,  and  the  omission  from  the  soap  kettle  of  fats  rich  in  palmitic, 
stearic  and  arachidic  acids;  for  the  same  reason  fats  containing 
in  essence  only  oleic,  linolic  and  similarly  constituted  acids 
are  used  for  such  soaps.  On  the  other  hand  a  hot  water  soap 
must  contain  the  higher  fatty  acids,  for  at  higher  temperatures 
the  lower  soaps  "  dissolve  "  and  pass  through  the  liquid  hydro- 
philic  colloid  state  into  true  solution  too  rapidly.  The  marine 
soaps  are  such  as  will  maintain  their  hydrophilic  colloid  properties 


188  SOAPS  AND  PROTEINS 

(and  consequently  will  wash)  even  in  relatively  highly  concen- 
trated salt  solutions,  like  sea  water.  The  ordinary  soaps  rich 
in  the  stearates  and  palmitates  are  useless  under  such  circum- 
stances, but  the  soaps  of  pure  cocoanut  oil  and  similarly  con- 
stituted fats  work  very  well,  for  their  entire  soap  series  is  largely 
unaffected  by  sodium  chlorid  of  the  concentration  found  in  sea 
water. 

The  settled  soaps,  which  are  smoother  and  decidedly  less  dry 
than  the  curd  soaps,  owe  these  properties  to  the  fact  that  they 
hold  more  water  than  the  latter.  In  the  curd  soaps  the  higher, 
more  solid  and  more  crystalline  soaps  tend  to  fall  out  within 
the  more  liquid  ones,  thus  making  for  non-homogeneous  soap 
mixtures.  When  through  such  less  perfect  salting-out  these  higher 
soaps  are  permitted  to  hold  a  larger  fraction  of  water  the  whole 
system  appears  clearer.  Because  of  the  higher  water  content 
100  parts  of  the  mixed  fats  commonly  yield  175  to  200  parts 
by  weight  of  finished  soap  of  the  settled  type. 

The  half-settled  soaps  and  the  soft  soaps  are  usually  made 
from  the  kettle  contents  direct.  They  differ  from  curd  and  settled 
soaps  in  containing  a  still  larger  fraction  of  water — commonly 
250  to  600  parts  of  finished  soap  being  obtained  from  100  parts 
of  fat.  The  water  in  these  soaps  is  held  in  part  in  the  soap  itself, 
in  equally  large  or  even  larger  fraction,  however,  as  water  joined 
to  filler.  The  filler  may  be  sodium  chlorid  but  commonly  it  is 
water-glass,  excess  alkali,  sodium  carbonate  or  sodium  borate, 
or  two  or  more  of  these  in  combination.  When  sodium  soaps 
are  filled  with  these  materials  a  final  product  is  obtained  which 
is  still  fairly  firm.  The  distinctly  soft  soaps  are  usually  potassium 
soaps  made  from  fats  and  fatty  acids  of  low  melting  points. 
These  may  be  and  are  filled  with  potassium  salts  so  that  the 
final  yield  may  be  as  great  as  ten  times  the  orginal  weight  of  the 
fat  used.  When  the  filling  of  potassium  soaps  is  carried  out  with 
sodium  salts  a  partial  conversion  to  sodium  soap  occurs  which 
tends  to  make  the  final  product  less  soft. 

§2 

In  connection  with  the  above  facts  which  show  how  much 
water  different  soaps  may  be  made  to  hold,  it  is  of  interest  to 
introduce  some  experiments  of  C.  STIEPEL  l  on  the  hygroscopic 
1  C.  STIEPEL:  Fette,  Oelc  und  Wachse,  usw.,  100,  Leipzig  (1911). 


THE  COLLOID-CHEMISTRY  OF  SOAP   MANUFACTURE    189 


properties  of  the  sodium  and  potassium  soaps  of  different  fatty 
acids.  STIEPEL  found  that  100  parts  of  the  following  dry  soaps 
would  take  up  from  the  air  the  following  number  of  parts  by  weight 

of  water: 

Potassium  oleate 162 

Potassium  palmitate 55 

Potassium  stearate .  .  30 


Sodium  oleate .... 
Sodium  palmitate 
Sodium  stearate . . 


12 
8 
7.5 


As  we  consider  the  water-holding  power  of  different  soaps 
against  the  forces  of  evaporation  of  much  biological  importance 
(since  the  metallic  fatty  acid  compounds  are  analogous,  in  our 
minds,  to  the  metallic  amino  (fatty)  acid  compounds  which 
make  up  protoplasm  l)  we  wish  to  insert  here  some  experiments 
on  the  rate  of  water  loss  by  various  soaps  when  exposed  to  ordi- 
nary atmospheric  conditions.  The  relationship  between  the 
chemical  constitution  of  a  soap  and  that  of  the  rate  at  which 
any  amount  of  water  it  holds  in  colloid-chemical  union  is  lost 
to  the  air  is  shown  by  the  following: 

When  10  grams  of  half  molar  "  solutions  "  of  different  soaps 
of  the  acetic  series  are  placed  in  low  evaporating  dishes,  10  cm. 
in  diameter,  and  allowed  to  lose  water  at  18°  C.,  the  relative 
percentages  of  weight  lost  at  the  end  of  seventy-two  hours  are 
as  indicated  in  Table  LVI.  There  is  obviously  an  inhibition  to 
water  loss  by  evaporation  as  the  acetic  series  is  ascended  and  a  greater 
water  loss  in  the  case  of  the  sodium  soaps  than  in  that  of  the  potassium 
soaps. 

TABLE   LVI 


Na 

K 

Propionate  

95.2 

93.0 

Butyrate 

92  0 

93  0 

Valerate 

93  0 

93  0 

Caproate 

91  0 

90  0 

Caprylate 

90.0 

91.4 

Caprate  . 

86.0 

88.0 

Laurate 

87.0 

87.0 

Myristate  

85.0 

83.0 

Palmitate  

83.0 

30.0 

Margarate  

85.4 

15.4 

Stearate  

79.0 

16.0 

1  Se«  page  205. 


190  SOAPS  AND  PROTEINS 

When  half  molar  "  solutions  "  of  sodium  and  potassium  oleate 
are  studied  under  similar  circumstances  the  values  differ  as 
follows : 

Na        K 
Oleate 86         81 

11.  The  Conversion  of  One  Soap  into  Another 

The  fact  previously  stated  that  one  metal  will  never  com- 
pletely displace  the  metal  from  another  soap  but  that  the  system 
will  merely  tend  to  the  production  of  a  state  of  equilibrium 
between  the  two  has  long  been  taken  advantage  of  in  various 
ways  in  practical  soap  manufacture,  both  in  the  direction  of  the 
production  of  a  less  "  soluble  "  soap  from  a  more  soluble  one 
and  vice  versa. 

Under  the  first  heading  may  be  cited  the  production  of  sodium 
soaps  from  potassium  soaps.  While  the  process  has  been  largely 
discarded,  it  remains  an  interesting  illustration  of  how,  empiri- 
cally, good  methods  are  followed  even  when  the  reasons  for  the 
practices  are  imperfectly  understood.  Especially  in  the  manu- 
facture of  sodium  "  tallow  "  soap  was  it  long  considered  best 
to  start  its  production  through  the  addition  of  caustic  potash 
to  the  "  tallow."  After  the  fat  was  converted  into  potassium 
soap,  this  was  changed  into  sodium  soap  and  subsequently  salted 
out  through  addition  of  sodium  chlorid.  It  is  self-evident  that 
the  procedure  in  reality  represents  the  production  of  a  potassium 
soap  followed  by  its  (partial)  decomposition  to  sodium  soap 
through  addition  of  the  sodium  salt,  and  the  subsequent  salting- 
out  of  this  mixed  potassium-sodium  soap  by  the  excess  of  sodium 
chlorid  mixed  with  the  potassium  chlorid  formed  through  double 
decomposition.  The  process  has  been  largely  discarded  in  this 
country  because  of  the  high  cost  of  potassium  hydroxid  and 
the  lower  cost  of  sodium  hydroxid,  but  it  is  a  question  whether 
in  so  doing  something  of  advantage  in  the  quality  of  the  soap 
produced  has  not  also  been  sacrificed.  The  "  tallow "  soaps 
(and  still  more  those  now  produced  from  hydrogenated  cotton- 
seed and  other  oils)  are  soaps  rich  in  the  higher  fatty  acids  (espe- 
cially palmitic  and  stearic)  and  to  produce  in  the  soap  kettle 
the  potassium  soaps  of  these  compounds  is  to  produce  such  as 
are  decidedly  more  soluble  (and  hence  more  quickly  obtained) 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    191 

than  the  corresponding  sodium  soaps.  But  even  after  the^r 
conversion  into  the  sodium  soaps,  those  made  by  the  indirect 
process  have  advantages  not  possessed  by  the  sodium  soaps 
produced  directly,  the  sodium  soaps  produced  by  the  indirect 
process  being  not  only  softer  and  smoother  but  being  generally 
more  satisfactory  in  the  matter  of  lathering  and  for  washing 
purposes  than  the  straight  sodium  soaps.  These  advantages 
are  dependent  upon  the  fact  that  through  indirect  manufacture 
the  potassium  soap  is  not  completely  converted  to  sodium  soap; 
it  continues  to  carry  admixed  a  certain  remnant  of  potassium 
soap,  the  technologic  advantage  of  which  over  the  sodium  soap 
is  particularly  marked  when  the  higher  fatty  acids  are  concerned. 

Advantage  of  these  general  truths  continues  to  be  taken  in  the 
present  day  manufacture  of  the  "  shaving "  soaps,  which  are 
essentially  only  carefully  neutralized  soaps,  which  in  addition  to 
sodium  carry  a  certain  amount  of  potassium  as  the  base  combined 
with  the  fatty  acids.  Because  of  their  content  of  potassium 
soaps,  especially  of  the  higher  fatty  acids,  the  shaving  soaps 
lather  more  easily  than  the  pure  sodium  soaps  and  are  subse- 
quently less  likely  to  "  dry  on  the  face." 

Various  patents  and  processes  are  known  to  the  soap  manu- 
facturer in  which  fats  and  oils  are  first  saponified  with  ammo- 
nium hydroxid  and  the  ammonium  soap  is  then  converted  into 
sodium  soap  through  addition  of  sodium  chlorid  or  sodium  car- 
bonate. The  underlying  principles  are  again  the  same;  the  advan- 
tages of  the  resulting  soap  are  again  those  of  having  admixed  in 
the  sodium  soap  a  certain  amount  of  "  more  soluble  "  ammo- 
nium soap. 

The  reverse  situation,  namely,  that  of  making  a  "  more  sol- 
uble "  soap  from  a  less  soluble  one  is  illustrated  in  the  P.  KREBITZ 
process  of  glycerin  and  soap  manufacture.  In  this  the  fat  or  oil 
is  first  converted  into  calcium  soap  by  boiling  it  with  caustic  lime. 
The  granular  calcium  soap  thus  produced  is  then  changed  to 
sodium  soap  through  the  addition  of  sodium  carbonate.  As  in 
the  previously  described  process,  in  which  a  certain  amount  of 
potassium  is  carried  over,  the  resultant  soap  in  this  instance 
carries  over  certain  of  the  attributes  of  the  original  calcium  soap. 
Soaps  made  by  this  process  are  therefore  dryer,  more  brittle, 
and  incline  to  be  whiter  than  the  corresponding  pure  sodium 
soaps  made  directly  from  the  same  fatty  acids. 


192  SOAPS  AND  PROTEINS 


II 
FILLERS  FOR  SOAPS 

The  extensive  use  of  various  fillers  in  the  manufacture  of  soaps 
necessitates  touching  upon  this  problem.  It  has  been  discussed 
from  many  points  of  view.  Various  inventors  and  manufac- 
turers have  been  honest  in  stating  that  the  primary  purpose  of 
such  fillers  is  to  meet  the  demand  for  "  cheap  "  soap.  Others,  to 
justify  the  procedure,  emphasize  the  improved  washing  charac- 
teristics of  such  soaps.  Thus,  a  certain  excess  of  alkali  is  actually 
necessary  in  the  soaps  used  for  cleansing  wool;  an  excess  of 
sodium  carbonate  acts  as  a  softener,  when,  as  is  commonly  the 
case,  untreated  water  containing  calcium  or  magnesium  is  used; 
water-glass,  so  commonly  used  to  fill  soaps,  has  colloid-chemical 
properties  similar  to  those  of  soap  itself.  On  the  other  hand, 
sugar  tends  to  keep  soaps  transparent,  while  various  sands  and 
pumice  give  them  abrasive  properties  which  may  be  of  serivce  in 
various  technologic  procedures.  The  fact  remains,  however,  that 
"  fillers  "  are  commonly  materials  decidedly  cheaper  than  soap 
itself,  that  they  tend,  in  general,  to  add  weight  or  water  to  the 
finished  product  and  that  in  most  instances,  as  one  of  our  soap 
chemist  friends  (C.  P.  LONG)  puts  it,  they  hasten  the  millennium 
when  the  soap  maker  will  be  able  to  "  get  a  bar  of  water  to  stand 
alone." 

Our  problem  is  fortunately  not  concerned  with  the  necessities 
or  the  moralities  of  the  situation,  but  with  the  question  of  what  the 
mixture  of  soap  with  these  materials  means  in  the  terms  of  colloid 
chemistry. 

Most  of  the  materials  used  to  fill  soaps  (exclusive  of  inconse- 
quential amounts  of  perfume,  various  coloring  substances  com- 
monly employed,  and  certain  "  dirt  "  solvents  like  naphtha)  may 
be  listed  with  some  one  of  the  following  three  groups. 

Group  I.  Sodium  chlorid,  sodium  carbonate,  sodium  borate 
and  sodium  silicate. 

Group  II.    Sugar  solutions. 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE     193 

Group  III. 

(A)  Potato  flour,  tapioca  meal,  starches  and  seed  husks. 

(B)  Clay,  barytes,  asbestos,  chalk  and  solutions  of  magnesium 
salts  (?) 

From  a  colloid-chemical  point  of  view,  it  is  easiest  to  dispose 
of  the  third  group  first.  With  the  exception  of  magnesium  sul- 
phate (which  might  more  correctly  be  placed  in  the  first  group) 
all  the  substances  used  are  earths  or  carbohydrates  which,  as 
employed,  are  largely  colloid  and  possessed  of  a  considerable 
capacity  for  hydration.  As  such  they  are  therefore  only  materials 
which,  when  mixed  with  the  soap,  increase  the  volume  of  what  is 
sold  to  the  public  as  soap.  This  does  not  mean,  of  course,  that, 
under  certain  circumstances,  the  sandlike  properties  of  some  of 
these  fillers  may  not  be  of  service  or  actually  necessary  in  various 
washing  processes.  Since  the  washing  properties  of  soaps  are  in 
large  measure  associated  with  their  properties  as  hydrated  col- 
loids and  as  such  properties  are  more  or  less  common  to  all  hy- 
drated colloids  whether  inorganic  (hydrated  clays)  or  organic 
(swollen  starch  grains),  this  fact  may,  of  course,  also  be  empha- 
sized. But  unless  the  composition  and  such  merits  or  demerits 
of  the  material  which  is  sold  to  the  public  as  soap  are  clearly 
stated,  the  motives  behind  their  use  cannot  be  held  to  be  higher 
than  those  always  incident  to  mere  substitution. 

With  the  market  price  of  sugar  what  it  is,  the  use  of  this 
material  as  a  filler  cannot  be  charged  to  any  desire  to  increase 
yield  while  decreasing  cost  of  production.  The  soaps  may  be 
"  loaded  "  with  the  sugars  (which  carry  with  them  not  only  high 
specific  gravity  but  also  a  certain  amount  of  water),  yet  the 
real  reason  for  their  use  seems  now  to  be  that  they  give  increased 
transparency  to  the  product.  How  the  sugars  accomplish  this 
is  not  yet  settled.  The  sugars  do  not  at  any  concentration 
"  salt-out  "  the  soaps  so  that  any  combination  of  the  sugar  with 
the  solvent  (as  so  frequently  discussed  in  the  case  of  the  salts) 
must  either  be  decidedly  less  or  of  a  different  type.  The  sugars 
clarify  soap/water  systems  as  do  alcohols  or  aldehyds,  which 
prompts  us  to  the  conclusion  that  they  have  an  action  like  the 
last-named  materials  and  so  really  owe  their  effects  to  the  fur- 
nishing of  such  a  substitute  "  solvent "  for  the  pure  water  more 
commonly  present  in  soap. 

In  the  substances  of  the  first  group,  we  deal  throughout  with 


194  SOAPS  AND  PROTEINS 

the  production  of  systems  similar  to  those  previously  discussed 
in  the  salting-out  of  soaps.1  The  addition  of  sodium  chlorid, 
sodium  carbonate,  sodium  borate  and  sodium  silicate  represents 
nothing  but  a  process  in  which  advantage  is  taken  of  the  fact  that  all 
these  materials  become  hydrated  and  emulsified  in  the  hydrated  soap, 
thus  yielding  a  stiffer  and  larger  amount  of  mixture  than  would  the 
soap  alone.  In  this  fashion  soaps  can  be  sold  with  a  larger  abso- 
lute water  content  and  still  appear  "  dry."  Beyond  this,  the 
merits  or  demerits  of  these  fillers  depend  upon  their  specific 
properties.  Sodium  chlorid  is  obviously  entirely  worthless, — 
it  has  no  "  softening  "  or  other  action  upon  water  and  its  presence 
interferes  with  the  development  of  the  washing  effects  of  all  soaps. 
Sodium  carbonate  and  sodium  borate  do  aid  in  the  first-named 
direction  and  any  excess  thus  unused  yields  an  overplus  of  alkali 
(after  hydrolysis  in  water)  which  in  its  turn  is  possessed  of  those 
advantages  which  any  alkali  may  show  in  specific  washing  proc- 
esses. The  same  may  be  said  of  sodium  silicate  (especially  of  the 
commercially  employed  "  water-glass ")  which  in  addition  to 
the  properties  already  mentioned  yields  colloid  silicic  acid  when 
diluted  in  the  process  of  washing.  The  colloid  silicic  acid  has 
some  of  the  properties  which  give  to  soap  itself  its  washing  char- 
acteristics. From  these  advantages  must,  however,  be  sub- 
tracted certain  disadvantages,  as  the  fixation  of  the  silicic  acid 
upon  the  washed  materials  and  their  "  felting/'  the  smarting  of 
the  skin  if  the  soap  is  used  for  toilet  purposes,  etc. 

How  sodium  chlorid  produces  the  "  fill  "  when  added  to  any 
soap  has  already  been  discussed.2  How  sodium  carbonate, 
sodium  silicate,  sodium  borate  and  magnesium  sulphate  act  in 
entirely  analogous  fashion  is  illustrated  for  two  pure  soaps  (sodium 
and  potassium  oleate)  in  Figs.  96  and  97  and  Tables  LVII,  LVIII, 
LIX,  LX,  LXI,  LXII,  LXIII  and  LXIV,  which  detail  the  experi- 
mental procedures  followed.  The  purpose  of  the  soap  maker 
is  to  obtain,  from  such  otherwise  liquid  mixtures  as  are  contained 
in  the  control  tubes  shown  at  the  extreme  right  of  all  these  series, 
the  solid  soaps  found  in  tubes  nearer  the  middle  of  each  of  the 
series.  The  exact  point  at  which  such  maximal  stiffening  of  the 
soaps  is  obtained  varies,  however,  both  with  the  type  of  soap 
initially  employed  (whether  a  sodium  or  a  potassium  soap,  for 
example)  and  the  nature  of  the  salt  used  as  "  filler."  At  the  same 
1  See  page  93.  »  See  page  113. 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE     195 

molar  concentration  sodium  carbonaie  is  least  effective,  sodium 
silicate  takes  a  middle  position  and  sodium  borate  is  strongest. 
The  photographs  (and  the  experimental  protocols)  show  how,  as 
these  different  salts  are  used,  the  gelation  point  is  shifted  further 
toward  the  left.  It  will  be  noted  that  sodium  borate  at  half  the 
concentration  of  sodium  silicate  produces  an  equal  degree  of  soap 
filling,  and,  also,  that  the  sodium  borate  is  as  powerful  in  ultimate 
effects  as  double  the  concentration  of  magnesium  sulphate.1 
It  is  questionable,  of  course,  whether  the  addition  of  magnesium 
sulphate  to  soap  has  any  justification  whatsoever  save  that  of 
giving  "  load."  Magnesium  sulphate  adds  nothing  to  water  which 
improves  its  washing  characteristics  and,  as  the  lowermost  series 
of  tubes  in  Figs.  96  and  97  show,  it  also  partially  decomposes 
the  sodium  or  potassium  soap  into  the  poorer  magnesium  soap. 

It  will  be  observed  in  comparing  the  two  figures  that  there  is 
a  shifting  of  the  gelation  point  toward  the  left  as  a  sodium  soap 
takes  the  place  of  an  equally  concentrated  potassium  soap.  This 
is  again  identical  with  the  similar  shift  observed  in  all  the  "  salting- 
out  "  experiments  previously  described. 

Ordinarily,  in  the  manufacture  of  the  filled  soaps,  the  addition 
of  water-glass,  borax  or  other  material  is  carried  to  the  highest 
point  possible  short  of  the  "  cracking  "  or  "  liquefying  "  of  the 
mixture,  or  the  "  salting-out  "  of  the  soap.  This  point  is  always, 
obviously,  somewhere  on  this  side  of  the  optimum  gelation  point. 
When  through  careless  mixing  or  error  in  judgment  the  filling  of 
a  soap  is  carried  beyond  this  critical  point  (represented  by  tran- 
sition from  the  system  salt-water-in-hydrated  soap  to  that  of 
hydrated-soap-in-salt-water)  what  is  to  be  done?  What  must 
be  accomplished  is  the  reversal  in  type  of  system  through  dilution  of 
the  salt  and  increase  in  the  absolute  amount  of  soap  in  the  system. 
The  proper  result  is  not  obtainable,  however,  through  mere 
addition  of  more  soap  and  water.  One  might  think  that  it  could 
be  obtained  by  heating  and  subsequently  cooling  the  mixture,  but 
the  soap  in  these  mixtures  is  near  the  "  stringing  "  point  and 
therefore  dangerous  to  heat;  or  the  added  compounds  are  of  a 
type  which  will  not  stand  boiling  without  suffering  hydrolysis 
and  permanent  decomposition.  The  best  way  to  proceed  is  to 

1  In  such  observations,  obviously,  lie  interesting  material  facts  covering 
the  matter  of  the  quantity  of  "hydration"  suffered  by  different  salts  in 
solution. 


196 


SOAPS  AND  PROTEINS 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    197 


198 


SOAPS  AND  PROTEINS 


dilute  the  spoiled  mixture  and  let  it  stand l  (thereby  diluting  the 
salt  and  allowing  the  soap  to  increase  its  hydration);  more  soap 
may  then  be  added  and  more  time  given.  This  may  by  itself 
accomplish  the  desired  end,  but,  if  it  does  not,  the  whole  batch 
should  be  mixed,  with  proper  stirring  and  sufficient  time,  into 
the  much  smaller  batch  of  soap/water  stock  thought  necessary 
for  the  production  of  the  correct  ultimate  system, 


TABLE   LVII 
SODIUM  OLEATE — Sodium  Carbonate 


Concentration  of  mixture. 

Remarks. 

(1)  5cc. 

m  sodium  oleate  +  9  cc.  HaO  +  l  cc.  m/2  NazCOj 

Mobile  liquid 

(2)   5cc. 

..       ..           .. 

+8cc. 

+2cc. 

Mobile  liquid 

(3)   5cc. 

i.        i.           .. 

+  7  cc. 

+3cc. 

Mobile  liquid 

(4)   5cc. 

••       ••           " 

+  6cc. 

+4cc. 

Viscid  liquid 

(5)  5cc. 

..                    ..                             4. 

+  5cc. 

+  5cc. 

Viscid  liquid 

(6)   5cc. 

4.                             44 

+4  cc. 

+  6cc. 

Very  viscid 

(7)   5cc. 

4.                             44 

+3cc. 

+  7cc. 

Solid  gel 

(8)   5cc. 

4.                    4.                              4. 

+2cc. 

+  8cc. 

Solid  gel 

(9)   5cc. 

44                    4.                             44 

+  lcc. 

+9cc. 

Solid  gel 

(10)   5cc. 

44                    44                             44 

+  10  cc.  m/2  NaiCOi 

Solid  gel 

(11)  5cc. 

+  10  cc.  HiO  (control) 

Mobile  liquid 

1  There  is  no  element  in  technologic  practice  involving  lyophilic  colloids 
which  is  less  considered  and  less  properly  employed  than  this  of  time.  The 
chemist  is  so  obsessed  by  the  theories  and  so  ruled  by  his  experience  with  the 
dilute  solutions  that  he  believes  that  his  colloid  mixtures  ought  to  act  similarly. 
Whenever  a  lyophilic  colloid  is  concerned  it  should  be  remembered  that  its 
solvation  or  its  desolvation  takes  all  the  time  which  may  be  included  in  a  proc- 
ess of  diffusion,  of  solution  and  of  chemical  union — and  these  things  are  rarely 
instantaneous.  Even  when  mixtures  are  correctly  made  from  a  quantitative 
standpoint,  the  result  may  be  worthless  if  proper  time  is  not  given  for  the 
physico-chemical  changes  necessary  to  yield  the  proper  ultimate  system. 


THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE     199 


TABLE   LVIII 

SODIUM  OLEATE — Sodium  Silicate 


Concentration  of  mixture. 

Remarks. 

(1)  5  cc.  m  sodium  oleate+9  cc. 

HzO  +  1  cc.  m/2  NazSiOa 

Mobile  liquid 

(2)  5  cc.  " 

'     +8  cc. 

"    +2cc.     " 

Less  mobile  liquid 

(3)  5  cc.  " 

"     +7cc. 

"    +3cc.     " 

Viscid 

(4)   5  cc.  " 

"     +6cc. 

"    +4cc.     " 

Very  viscid 

(5)  5  cc.  " 

"     +5cc. 

"    +5cc.     " 

Solid  gel 

(6)  5  cc.  " 

"     +4  cc. 

"    +6cc.     " 

Solid  gel 

(7)  5cc.  " 

"     +3cc. 

"    +7cc.     " 

Beginning  separation 

(8)   5cc.  " 

"     +2  cc. 

"    +8cc.     " 

Great  dehydration  and  separa- 

tion 

(9)   5  cc.  " 

"     +lcc. 

"     +9  cc.     " 

Great  dehydration  and  separa- 

tion 

(10)   5cc.  " 

"     +10cc 

.  m/2  NazSiOs 

Great  dehydration  and  separa- 

tion 

(11)   5cc.  " 

'  '      +  10  cc 

.  HzO  (control) 

Mobile  liquid 

TABLE   LIX 

SODIUM  OLEATE — Sodium  Borate 


Concentration  of 

mixture. 

Remarks. 

(1)  5cc. 

m  sodium  oleate+9  cc.  HzO  +  1  cc.  m/4  NazB^T 

Mobile  liquid 

(2)  5cc. 

+8cc. 

"    +2cc.     ' 

White,  milky,  mobile  liquid 

(3)  5cc. 

"       "           "     +7cc. 

"    +3cc.     " 

While,  milky,  mobile  liquid 

(4)   5cc. 

+  6cc. 

"    +4cc.     " 

Milky  soap  on  top,   water  on 

bottom 

(5)   5cc. 

"     +5cc. 

"    +5cc.     " 

Milky  soap  on  top,   water  on 

bottom 

(6)   5cc. 

"      +4cc. 

"    +6cc.     " 

Milky  soap  on  top,  water    on 

bottom 

(7)   occ. 

'  +3cc. 

"    +7cc.     " 

Milky  soap  on  top,   water  on 

bottom 

(8)   Sec. 

"      +2cc. 

"    +8cc.     " 

Milky  soap  on  top,  water  on 

bottom 

(9)  5cc. 

"      +lcc. 

"    +9cc.     " 

Yell,w    soap    on    top,    much 

water  on  bottom 

(10)  See. 

+10  cc. 

m/4  Na2B4O7 

Yellow    soap    on    top,    much 

water  on  bottom 

(11)   5cc. 

+10  cc. 

H2O  (control) 

Mobile  liquid 

200 


SOAPS  AND  PROTEINS 


TABLE   LX 
SODIUM  OLEATE — Magnesium  Sulphate 


Concentration  of 

mixture. 

Remarks. 

(1)  See. 

m  sodium  oleate  +  9  .  5  cc. 

H2O  4-0  .  5  cc.  m/2  MgSO4 

Fairly  mobile  milky  liquid 

(2)   5cc. 

•'                   "     4-9.  Occ. 

"    +  1.0cc.    " 

Solid  white  gel  mixture 

(3)   5cc. 

"     +8.5cc. 

"    4-1.  occ.    " 

Solid  white  granular  gel 

(4)   5cc. 

"     4-8.  Occ. 

"    +2.0cc.    " 

Solid  white  granular  gel 

(5)   See. 

-1-7.  5  cc. 

"    -f2.5cc.    " 

Granular  white  soap,  beginning 

separation 

(6)  5cc. 

4-7.  Occ. 

"    4-3.  Occ.    " 

Granular  white  soap,  more  sep- 

aration 

(7)   5cc. 

H-6.  5cc. 

"    +3.5cc.    " 

Granular  white  soap,  more  sep- 

aration 

(8)  5cc. 

"      +6.0cc. 

"    4-4.  Occ.    " 

Granular  white  soap,  more  sep- 

aration 

(9)  5cc. 

"       "           "     4-5.  5cc. 

"    +4.5cc.    " 

Granular  white  soap,  more  sep- 

aration 

(10)  See. 

+5.0cc. 

"    4-5.  Occ.    " 

Granular  white  soap,  more  sep- 

aration 

(11)   5cc. 

"      +  10.  0  cc.  HiO  (control) 

Mobile  liquid 

TABLE   LXI 
POTASSIUM  OLEATE — Sodium  Carbonate 


Concentration  of  mixture. 

Remarks. 

(1)  See. 

m  potassium  oleate  +9  cc.  HtO  +  1  cc.  m/2  NazCOa 

Mobile  liquid 

(2)  5cc. 

"     4-8  cc.     "    +2  cc.    " 

Mobile  liquid 

(3)   5cc. 

"     +7  cc.     "    4-3  cc.    " 

Mobile  liquid 

(4)  5cc. 

"     4-6  cc.     "    4-4  cc.    " 

Mobile  liquid 

(5)   5cc. 

"     4-5  cc.     "    +5  cc.   " 

Mobile  liquid 

(6)  See. 

"     +4  cc.     "    4-6  cc.   " 

Less  mobile  liquid 

(7)  5cc. 

"     4-3  cc.     "    4-7  cc.   " 

Viscid  liquid 

(8)  5cc. 

"     4-2  cc.     "    +8  cc.   " 

Very  viscid  liquid 

(9)   5cc. 

"     4-1  cc.     "    +9  cc.   " 

Almost  stiff 

(10)   Sec. 

"      +10  cc.  m/2  NazCOi 

Almost  stiff 

(11)  5cc. 

"          "             "     4-10  cc.  HiO  (control) 

Mobile  liquid 

THE  COLLOID-CHEMISTRY  OF  SOAP  MANUFACTURE    201 

TABLE   LXII 
POTASSIUM  OLEATE — Sodium  Silicate 


Concentration  of  mixture. 

Remarks. 

(1)   5cc. 

m  potassium  oleate  +  9  cc.  HjO  +  1  cc.  m/2  NasSiOi 

Mobile  liquid 

(2)   5cc. 

"           •  • 

1      +8cc.     "    +2cc.     ' 

Mobile  liquid 

(3)   5cc. 

,. 

"     +7cc.     "    +3cc.    " 

Mobile  liquid 

(4)   See. 

" 

"     +6cc.     "    +4  cc.    " 

Mobile  liquid 

(5)   5cc. 

,, 

"     +5  cc.     "    +5  cc.    " 

Viscid  liquid 

(6)  5cc. 

«                           4  > 

"     +4cc.     "    +6cc.    " 

Viscid  liquid 

(7)  5cc. 

"                           " 

"     +3cc.     "    +7cc.    " 

Viscid  liquid 

(8)  5cc. 

"                           " 

"     +2cc.     "    +8cc.    " 

Solid  gel 

(9)  5cc. 

4.                           44 

"     +lcc.     "    +9cc.    " 

Solid  gel 

(10)   5  cc. 

4. 

"     +10cc.  m/2  NaiSiOj 

Viscid  liquid 

(11)   5cc. 

"     +10  cc.  HzO  (control) 

Mobile  liquid 

TABLE    LXIII 

POTASSIUM  OLEATE — Sodium  Borate 


Concentration  of  mixture. 


Remarks. 


(1)   5cc. 

m  potassium  oleate+9  cc. 

HiO  +  1  cc.  m/4  NazB4O7 

Clear  mobile  liquid 

(2)   5cc. 

"      +8cc. 

"    +2cc.     "           "     , 

Cloudy  mobile  liquid 

(3)   See. 

"     +7cc. 

"    +3cc.    " 

Milky  mobile  liquid 

(4)   5cc. 

"     +6cc. 

"    +4cc.    M 

Milky  mobile  liquid 

(5)   5cc. 

"     +5cc. 

"    +5cc.    "           "     ' 

Milky  mobile  liquid 

(6)  5cc. 

"     +4cc. 

"    +6cc.    " 

Milky,  less  mobile  liquid 

(7)  5cc. 

"     +3cc. 

"    +7cc.    " 

Milky  viscid  liquid 

(8)   5cc. 

«•             "     +2cc. 

"    +8cc.    " 

Milky,  almost  stiff 

(9)   5cc. 

"     +lcc. 

"    +9  cc.    " 

Milky,  almost  stiff 

(10)   5cc. 

"     +10cc.  m/4  NaiB«O7 

Milky,  almost  stiff 

(11)  See. 

"     +10  cc 

.  HiO  (control) 

Mobile  liquid 

TABLE   LXIV 

POTASSIUM  OLEATE — Magnesium  Sulphate 


Concentration  of  mixture. 


Remarks. 


(1)  5  cc.  m  potassium  oleate+9 . 5  cc.  HiO  +0 . 5  cc.  m/2  MgSO4 


(2)  5  cc.  " 

(3)  5  cc.  " 

(4)  See." 

(5)  Sec." 

(6)  5cc.  " 

(7)  5  cc.  " 

(8)  5  cc.  " 

(9)  See." 

(10)  5cc.  " 

(11)  5cc.  " 


+9.0cc. 

"    +1.0cc.     ' 

+8.5cc. 

"    +1.5cc.     ' 

+  8.0cc. 

"    +2.0cc.     ' 

+  7.5cc. 

"    +2.5cc.     ' 

+7.0cc. 

"    +3.0cc.     ' 

+  6.  See. 

"    +3.5cc.     ' 

+  6.0cc. 

"    +4.0cc.    ' 

+5.  See. 

"    +4.  See.    ' 

+5.0cc. 

"    +5.0cc.    ' 

+  10.0cc. 

H»O  (control) 

Fairly  mobile  milky  liquid 
Viscid  milky  liquid 
Solid  milky  gel 
Solid  milky  gel 
Solid  white  soap  at  top 
Solid  white  soap  at  top 
Solid  white  soap  at  top 
Solid  white  soap  at  top 
Solid  white  soap  at  top 
Solid  white  soap  at  ton 
Mobile  liquid 


PART  THREE 

THE    ANALOGIES    IN    THE    COLLOID-CHEMISTRY  OF 
SOAPS,  PROTEIN  DERIVATIVES  AND   TISSUES 


PART  THREE 

THE   ANALOGIES   IN    THE    COLLOID-CHEMISTRY   OF 
SOAPS,   PROTEIN  DERIVATIVES  AND   TISSUES 


THE  CHEMICAL  AND  COLLOID-CHEMICAL  BEHAVIOR  OF 
FATTY  ACIDS  AND  THEIR  DERIVATIVES  AND  THE 
ANALOGOUS  BEHAVIOR  OF  "NEUTRAL"  PROTEINS 
AND  THEIR  DERIVATIVES 

1.  Introduction 

THE  experiments  on  the  colloid-chemistry  of  the  various  pure 
soaps  detailed  in  the  preceding  pages  were  undertaken  originally 
in  order  to  obtain  a  clearer  conception  of  the  nature  of  water 
absorption  by  proteins  when  various  alkalies,  acids  or  salts,  alone 
or  in  combination,  are  added  to  them;  this  conception  being 
wanted,  in  its  turn,  in  order  to  understand  the  laws  of  water 
absorption  as  observed  in  living  matter.  It  will  be  the  purpose 
of  the  next  paragraphs  to  show  that  the  laws  emphasized  as  govern- 
ing the  "  solution  "  and  "  hydration  "  of  soaps  are  identical  with 
those  which  govern  the  "  solution  "  and  "  hydration "  of  various 
protein  derivatives  and  that  thesey  in  turn,  are  the  analogs  of  the  laws 
which  govern  the  absorption  of  water  by  cells,  tissues  and  the  whole 
living  organism  under  physiological  and  pathological  circumstances. 

2.  The  Chemical  Behavior  of  the  Fatty  Acids  and  the  Analogous 
Behavior  of  the  Ammo-Acids  (Neutral  Proteins) 

It  is  well  to  emphasize,  first,  some  obvious  chemical  analogies 
existent  between  the  fatty  acids  and  the  materials  which  may  be 
derived  from  them  (the  soaps)  and  the  so-called  "  neutral " 

205 


206  SOAPS  AND  PROTEINS 

proteins  and  the  materials  which  may  be  produced  from  them. 
It  is  of  interest  to  bear  in  mind  that  the  proteins  are  not  only 
polymerized  amino-acids,  but  that  frequently  their  constituent 
amino-acids  are  amino-fatty-acids,  as  witness,  amino-acetic, 
amino-valeric,  amino-caproic  and  amino-succinic  acids.  The 
alleged  "  neutral"  "  native  "  or  "  genuine  "  proteins  are  no  more 
neutral  than  are  any  of  the  higher  fatty  acids.  As  the  fatty  adds  may 
combine  with  base  to  form  "  soaps,"  even  so  may  the  polymerized 
amino-fatty-acids  combine  with  base  to  form  analogous  "  soap- 
like  "  compounds.  It  is  important  for  our  future  discussion  that 
this  comparison  of  the  neutral  proteins  with  the  free  fatty  acids 
be  clearly  kept  in  mind.1 

What,  now,  are  the  solubility  characteristics  of  the  pure  fatty 
acids  and  the  pure  neutral  proteins  in  water  and  for  water? 
Just  as  certain  fatty  acids  (like  the  lowermost  members  of  the 
acetic  series)  are  readily  soluble  in  water,  so  also  do  certain  native 
proteins  prove  "  soluble  "  in  water  (as  witness  the  various  salt-, 
acid-  and  alkali-free,  "pure"  albumins).  On  the  other  hand, 
as  other  fatty  acids  (like  the  higher  members  of  the  acetic  series) 
prove  insoluble  in  water,  so  also  do  various  native  proteins  (as 
witness  casein,  fibrin,  alkali-,  acid-  and  salt-free  globulins,  etc.). 

The  solubility  of  water  in  the  fatty  acids  or  in  the  pure  pro- 
teins is  hardly  to  be  found  discussed  as  such.  The  simpler  fatty 
acids  "  dissolve "  so  readily  in  water  and  are  so  universally 
thought  of  as  "  aqueous  solutions  "  that  the  mere  raising  of  the 
obverse  question  in  their  case  will  seem,  to  many,  absurd.  Water 
is,  however,  sufficiently  souble  in  the  higher  fatty  acids  to  make 
necessary  its  consideration,  when,  commercially,  a  given  weight 
or  volume  of  material  is  to  be  bought  and  paid  for  as  fatty  acid. 
In  the  case  of  the  pure  proteins  these  things  are  variable.  In 
those  commonly  designated  as  "  insoluble  "  (casein,  for  example) 
the  solubility  for  water  is  so  low  as  to  be  generally  neglected. 

1  Of  great  interest  in  connection  with  this  similarity  between  the  colloid- 
chemistry  of  the  fatty  acids  and  that  of  the  amino-fatty-acids  (the  proteins) 
are  some  observations  of  KRAFFT  and  WIGLOW  [quoted  by  LEWKOWITSCH: 
Oils,  Fats  and  Waxes,  1,  133  (1913)]  whose  work  unfortunately  we  have  not 
been  able  to  find  in  the  original.  These  authors  note  that  the  amins  of  the 
fatty  acids  behave  like  the  corresponding  fatty  acids.  While  the  alkali  salts  of 
the  lower  amino-fatty-acids  on  solution  in  water  behave  like  crystalloids, 
those  of  the  higher  amino-fatty-acids  fail  to  raise  the  boiling  point  of  water 
the  calculated  amount  and  in  other  physico-chemical  respects  betray  them- 
selves as  colloids. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES 


207 


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208  SOAPS  AND  PROTEINS 

From  this  it  may  rise  to  great  values,  as  witness  the  amount 
of  fluid  "  absorbed  "  by  neutral  gelatin,  by  dry  serum-albumin, 
etc.,  when  these  are  thrown  into  water. 

These  characteristics  of  solubility  in  water  and  for  water  of  the 
different  fatty  acids  and  the  different  pure,  "  neutral  "  proteins 
must  be  kept  in  mind  if  their  colloid-chemistry  or  that  of  their  deriva- 
tives is  to  be  properly  understood. 

If  we  now  write  the  formula  of  any  fatty  acid  as : 

z-COOH 

then  that  of  any  amino-fatty-acid  (or  its  polymer,  protein)  may 
be  written: 

z-COOH 

i 
NH2 

To  produce  a  "  soap,"  some  base  is  substituted  for  the  H  in  the 
first  formula  written  above;  to  produce  the  analogous  "  soap- 
like  "  compound  from  the  latter,  the  same  base  is  substituted  for 
the  similarly  placed  H  of  the  second  formula.  As  we  produce 
potassium,  sodium,  calcium  and  iron  soaps  we  can  also  produce 
potassium,  sodium,  calcium  and  iron  proteinates. 

Every  new  soap  and  every  new  soap-like  compound  thus  pro- 
duced has  solubility  characteristics  in  water  and  for  water  different 
from  those  of  the  original  fatty  acid  or  the  original  amino-fatty-acid 
(protein)  from  which  it  was  produced. 

The  amino-acids  have,  however,  wider  possibilities  for  easy 
union  with  other  materials  than  have  the  fatty  acids.  While 
the  latter,  for  example,  do  not  unite  readily  with  acids,  the  former, 
through  their  NH2  groups,  do.  In  this  way  there  may  therefore 
be  produced  a  second  series  of  derivatives  which  may  be  desig- 
nated as  the  chlorids,  bromids,  acetates,  sulphates,  phosphates, 
etc.,  of  the  proteins,  each  again  possessed  of  its  own  solubility 
in  water  and  solvent  power  for  water. 

We  are  now  in  a  position  to  consider  the  colloid-chemistry 
of  the  pure  proteins  and  that  of  their  basic  and  acidic  derivatives, 
not  only  to  see  how  these  mimic  the  colloid-chemical  behavior 
of  the  pure  fatty  acids  and  their  basic  derivatives  (the  soaps) 
but  in  order  to  obtain  what  seems  to  us  a  simpler  general  con- 
ception of  what  happens  when  protein/water  mixtures  show  the 
evidences,  under  different  circumstances,  of  swelling,  gelation, 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  209 

precipitation,  irreversible  "  coagulation,"  etc.  A  detailed  con- 
sideration of  many  proteins  is  impossible  within  the  pages  of  this 
volume,  but  the  two  to  be  discussed  may  serve  to  illustrate  the 
main  types.  For  purposes  of  illustration  we  shall  take  up,  in 
analogy  to  the  similar  types  of  pure  fatty  acids,  (a)  a  protein 
which  is  "  insoluble  "  in  water,  namely,  egg-globulin  and  (6) 
another  which  is  "  soluble,"  namely,  gelatin.  What  is  said  of 
egg-globulin  may  be  taken  to  apply  to  all  the  globulins,  casein, 
myosin  and  nucleic  acid.  What  is  said  of  gelatin  may  be  applied 
to  the  various  albumins.1 

3.  The  System  Egg-Globulin/Water 

The  "  neutral  "  globulin  used  in  the  experiments  about  to 
be  described  was  obtained  by  diluting  strongly  with  distilled  water 
(8  volumes)  the  whites  of  absolutely  fresh  eggs.  The  globulin 
which  fell  out  at  the  end  of  twenty-four  hours  in  an  ice  box  was 
simply  filtered  off,  washed  several  times  with  distilled  water  and 
used  at  once  in  its  moist  condition.  While  by  more  elaborate 
methods  a  "  chemically  "  purer  product  might  have  been  obtained, 
we  feared  the  consequences  of  the  more  drastic  chemical  methods 
necessary  to  produce  such  upon  the  colloid  properties  of  the 
final  product.  The  globulin  employed  in  the  following  experi- 
ments was  all  from  the  same  lot,  contained  92  percent  water 
as  used  and  0.045  percent  ash  calculated  upon  the  wet  weight 
of  the  globulin. 

Moist  globulin  (in  analogy  to  the  higher  fatty  acids)  is  obvi- 
ously "  insoluble  "  in  water  and  as  compared  with  gelatin,  albumin, 
etc..  a  relatively  poor  solvent  for  water  (92  percent).  We  wished, 
first,  to  show  that  a  soap-like  compound  (a  basic  globulinate) 
could  be  obtained  from  such  globulin  through  treatment  with 
a  proper  alkali,  which,  in  the  presence  of  the  right  amount  of  water 
would  (like  the  corresponding  soap)  yield  a  solid  jelly,  in  other 

1  The  purest  gelatins  on  which  the  ordinary  colloid-chemical  studies  have 
been  made,  to  which  we  refer  here  and  upon  which  some  succeeding  experi- 
ments are  based  (see  page  218)  still  contain  traces  of  salts.  WOLFGANG 
OSTWALD  has  directed  my  attention  to  the  fact  that  when  such  gelatins  are 
subjected  to  dialysis  while  an  electric  current  is  passed  through  thein  a  gelatin 
free  from  all  base  and  acid  may  be  obtained.  Such  gelatin  is,  however,  as 
"insoluble"  in  water  and  as  little  hydratable  as  the  ordinary  globulins. 
Obviously,  under  such  circumstances,  the  behavior  of  all  the  proteins  (includ- 
ing in  other  words  gelatin  and  the  "albumins")  becomes  that  of  the  type 
described  under  the  globulins. 


210  SOAPS  AND  PROTEINS 

words,  a  system  representing  a  "  solution  "  of  water  in  the  basic 
globulinate.  For  this  purpose  2  grams  of  the  moist  globulin 
were  carefully  weighed  into  each  of  a  number  of  test  tubes  and  to 
each  was  then  added  0.5  cc.  of  an  alkali  of  proper  strength  to 
yield  the  final  concentration  in  the  whole  of  each  of  the  systems 
indicated  in  Table  LXV.  The  descriptions  refer  to  the  appear- 
ances of  the  mixtures  at  the  end  of  twenty-four  hours,  twenty 
of  which  were  spent  in  an  ice  box  and  four  at  room  temperature. 
The  photographic  appearance  of  the  three  sets  of  tubes  (all 
made  at  the  same  time,  from  the  same  globulin  and  under  iden- 
tical circumstances)  is  shown  in  the  Figs.  98,  99  and  100.  It  is 
apparent  that  these  potassium,  sodium  and  barium  globulinates 
(like  the  corresponding  soaps)  have  greater  solvent  powers  for 
water  (and  hence  gel  in  the  presence  of  a  larger  volume  of  the  same) 
than  has  the  original  "  neutral  "  globulin  (or  the  original  fatty 
acid).  But  of  the  three  soap-like  compounds  the  potassium 
globulinate  is  most  soluble  in  water,  wherefore  it  is  the  first  to 
go  through  a  jellying  stage  "  into  solution."  Sodium  globulin- 
ate  occupies  a  middle  position  in  this  regard.  Barium  globulinate, 
while  possessed  of  relatively  low  powers  of  hydration  is  so  insolu- 
ble in  water  that  it  maintains  its  gel  state  throughout  the  series 
of  experiments. 

Having  seen  that  with  progressive  additions  of  alkali,  neutral 
globulin  in  the  presence  of  a  fixed  volume  of  water  passes  suc- 
cessively from  (1)  a  (relatively)  non-hydrated  material  through 
(2)  a  state  in  which  water  is  dissolved  in  it,  into  (3)  a  state  in 
which  it  is  dissolved  in  the  water,  we  wished  to  see  what  were  the 
effects  of  mere  dilution  upon  the  final  system  and  if  the  basic 
globulinate  thus  formed  could  be  precipitated  a  second  time 
(salted-out)  by  further  addition  of  the  alkali  (as  can  a  soap).  Fig. 
101  and  Table  LXVI  answer  these  questions.  The  first  five  tubes 
merely  show  again  how  with  progressive  increase  in  amount  of 
alkali  (sodium  hydroxid),  "  solution  "  of  a  "  globulin  "  (really 
solution  of  sodium  globulinate)  may  be  obtained.  To  such  a  tube 
as  4  much  water 1  may  now  be  added  without  change,  as  evidenced 

1  Not,  however,  an  unlimited  amount,  for  in  too  much  water  hydrolysis 
of  the  sodium  globulinate  takes  place  and  the  free  acid  (globulin)  again  begins 
to  fall  out.  This  constitutes  the  principle  upon  which  "globulins"  are 
obtained  through  dilution  with  much  water.  It  is  not  the  sodium  globulitmtc 
which  falls  out,  or,  in  the  terms  of  soap  chemistry,  it  is  not  "the  soap"  which 
is  "insoluble"  in  water  but  the  "fatty  acid"  resulting  from  hydrolysis. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  211 


212 


SOAPS  AND  PROTEINS 


TABLE   LXVI 
EGG-GLOBULIN  AND  SODIUM  HYDROXID 


Tube 
number. 

Concentration  of  mixture. 

Remarks. 

Control       2  gms. 

moist  globulin  +0.5  cc.  IkO 

White  flocculent  precipitate 

1             2  gms. 

+0.5  cc.  1/10  n  NaOH 

Solid  gel 

2             2  gms. 

+0.5cc.  2/10n 

Clear  viscid  liquid 

3             2  gms. 

+0.5  cc.  3/10  n 

Clear  viscid  liquid 

4             2  gms. 

+0.5cc.    12  n 

Clear  liquid 

5             2  gms. 

+5.0  cc.      8  n 

Clear  liquid 

6             2  gms. 

+  5.0cc.      9n 

Clear  liquid 

7            2  gms. 

+5.0cc.     lOn 

Cloudy  liquid 

8             2  gms. 

+5.0cc.     11  n 

Partial  salting-out 

9            2  gms. 

"        +5.0cc.     12n 

Complete  salting-out 

TABLE  LXVI1 
EGG-GLOBULIN  AND  ACIDS 


Control  (H20). 

Acid. 

Final  concentration  of  the  acid  in  the  system. 

1/500  n 

2/100  n 

5/100  n 

10/100  n 

15/100  n 

White  flocculent  pre- 
cipitate 

Hydro- 
chloric 

White 
flocculent 
precipi- 
tate 

White 
flocculent 
precipi- 
tate 

White 
flocculent 
precipi- 
tate 

White 
flocculent 
precipi- 
tate 

White 
flocculent 
precipi- 
tate 

White  flocculent  prej 
cipitate 

Lactic 

White 
flocculent 
precipi- 
tate 

White 
flocculent 
precipi- 
tate 

White 
flocculent 
precipi- 
tate 

Slightly 
hydrated 
precipi- 
tate 

Slightly 
hydrated 
precipi- 
tate 

Control  (HzO). 

Acid. 

Final  concentration  of  the  acid  in  the  system. 

20/100  n 

40/100  n 

60/100  n 

80/100  n 

100/100  n 

White  flocculent  pre- 
cipitate 

Hydro- 
chloric 

Hydrated 
precipi- 
tate 

Hydrated 
precipi- 
tate 

Hydrated 
precipi- 
tate 

Hydrated 
precipi- 
tate 

Hydrated 
precipi- 
tate 

White  flocculent  pre- 
cipitate 

Lactic 

Hy.Irated 
precipi- 
tate 

Hydrated 
precipi- 
tate 

Gel 

Gel 

Gel 

SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES 


213 


in  tube  5  of  Fig.  101.  But  if  in  such  a  volume  of  water  the  con- 
centration of  alkali  is  progressively  increased  the  sodium  globu- 
linate  (commonly  and  wrongly  designated  "  globulin  ")  begins  to 


FIGURE  101. 

fall  out  until  complete  separation  from  the  dispersion  medium  is 
obtained  (see  the  tubes  7,  8  and  9). 

Figs.  102  and  103,  with  Table  LXVII,  show  that  when  the 
"  neutral  "  globulin  is  converted  into  a  chlorid  or  lactate  (for 
which  chemical  change  there  is  no  analog  in  the  case  of  the  pure 


FIGURE  102. 


FIGURE  103. 

fatty  acids)  these  compounds  are  again  better  solvents  for  water 
than  the  original  globulin,  in  consequence  of  which  the  tube  con- 
tents again  gel.  The  successive  acid  tubes  of  Figs.  102  and  103 
may  be  compared  with  the  alkali  tubes  of  the  same  concentrations 
of  Figs.  98,  99  and  100.  Experimental  procedure  was  the  same  in 


214  SOAPS  AND  PROTEINS 

both.  It  should  only  be  noted  that  the  concentrations  marked 
on  the  labels  of  Figs.  102  and  103  are  those  of  the  acid  as  added. 
The  final  concentrations  are  given  in  Table  LXVII. 

Such  experimental  findings  as  have  just  been  described  are 
more  commonly  listed,  as  by  the  physiological  chemists,  as  experi- 
ments on  the  "  solubility  "  of  proteins;  or  by  the  physical  and 
colloid-chemists  as  studies  on  the  effects  of  alkalies  and  acids  upon 
such  "  solubility  "  or  some  other  of  the  general  chemical  or  colloid- 
chemical  properties  of  the  systems  as  a  whole  (as  their  viscosity, 
their  electrical  conductivity,  their  content  of  hydrogen  and 
hydroxyl  "  ions,"  etc.).  To  understand  these  systems  properly 
it  is  obviously  necessary  to  recognize  and  carry  in  mind  the  effects 
of  (a)  the  quantitative  relationships  of  the  water  content  of  the 
systems  to  the  remaining  material  in  them,  (6)  the  chemical  con- 
versions of  "  neutral  "  compounds  into  basic  or  acidic  derivatives, 
(c)  the  alterations  in  solubility  and  hydration  capacity  accompany- 
ing such  conversion,  (d)  the  types  of  systems  produced  (whether 
all  hydrated  colloid,  all  solution  in  water  or  subdivisions  of  the 
one  in  the  other)  and  finally  (e)  the  changes  in  viscosity  incident 
to  "  emulsification "  or  "  suspension "  of  any  of  the  original 
unchanged  "  globulin  "  in  such  hydrated  derivatives  as  may  be 
produced.  How  inadequate  for  the  understanding  of  the  colloid- 
chemical  behavior  of  such  systems  are  the  overplayed  "  stoichio- 
metrical,"  "  chemical,"  "  electrical,"  "  hydrogen  and  hydroxyl 
ion  "  notions,  usually  called  upon  to  explain  in  some  exclusive 
fashion  all  the  changes  observed,  must  be  self-evident. 

Stoichiometrical  views  cover  only  those  parts  of  the  whole 
problem  which  have  to  do  with  the  quantities  produced  of  dif- 
ferently hy datable  or  soluble  compounds;  "  chemical  "  notions 
are  no  more  adequate  for  the  explanation  of  the  problem  than 
they  are,  at  present,  for  the  understanding  of  the  whole  problem 
of  solution;  electrical  and  ionic  notions  are  "hardly  of  service  when 
it  is  remembered  that  the  most  stabile  of  these  hydrated  colloid 
systems  are  such  as  are  composed  of  chemically  produced,  really 
neutral  compounds  of  protein  with  base  or  acid,  provided  only  that 
not  more  water  is  present  in  the  system  than  can  be  absorbed  by 
the  hydration  capacities  of  the  protein  derivatives.  Yet  these 
colloid  systems  contain  no  quantities  of  either  hydrogen  or  hydroxyl 
ions  measurable  by  ordinary  laboratory  means.  The  measurable 
hydrogen  and  hydroxyl  ion  contents  of  different  protein/ water  systems 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  215 

upon  which  such  emphasis  has  been  laid  for  the  explanation  of  their 
stability  are  only  observable  in  relatively  dilute  systems;  the  ion 
contents  are  not  inherent  to,  or  necessary  for,  the  stabilization;  they 
are  accidental  accompaniments  incident  to  the  solution  of  some  of  the 
basic  and  acidic  proteins  in  the  excess  of  water  and  their  hydrolysis 
with  the  production  secondarily  of  an  overplus  of  hydrogen  or  hydroxyl 
ions. 

Evidence  for  the  general  truth  of  these  contentions  may  be 
found  in  the  following  experiments  in  which  "  neutral  "  globulin 
in  the  presence  of  a  constant  volume  of  water  is  exposed  to  the 
action  of  various  neutral  salts.  As  ordinarily  put,  such  "  neu- 
tral "  globulins  are  said  to  be  "  soluble  "  in  dilute  salt  solutions. 
To  our  minds,  this  is  not  true.  The  salts  again  react  with  the 
neutral  globulin  to  yield  globulin  derivatives  of  the  general 
formula  base-protein-acid  which,  like  the  previously  described 
base-protein  and  protein-acid  compounds,  also  have  a  higher 
hydration  capacity  and  a  greater  solubility  in  water  than  the 
original  globulin. 

Figs.  104,  105,  106,  107  and  108  reproduce  photographically  the 
findings  described  in  Table  LXVIII.  Obviously  a  hydration  of 
"neutral"  globulin  may  be  induced  through  the  presence  of  various 
neutral  salts  as  readily  as  through  the  presence  of  alkalies  or  acids, 
in  other  words,  in  the  absence  of  any  such  hydroxyl  or  hydrogen 
ion  concentrations  as  are  commonly  alleged  to  be  responsible  for 
such  a  result.  It  is  not  the  neutral  globulin  which  is  hydrated, 
but  its  salts.  In  the  experiments  just  described,  these  are  pro- 
duced because  globulin  (like  the  lower  fatty  acids  of  the  acetic 
series)  has  sufficient  chemical  reactivity  to  unite  with  the  products 
of  the  hydrolysis  of  any  neutral  salt  (acid  and  alkali). 

Table  LXVIII  and  the  figures  again  show  (in  analogy  to  the 
similar  soaps)  that  the  potassium  and  sodium  derivatives  of  glob- 
ulin are  sooner  and  more  highly  hydrated  than  the  corresponding 
magnesium  and  calcium  derivatives  (the  contents  of  the  tubes 
holding  the  latter  being  not  only  less  swollen  but  whiter).  The 
mercury  derivative  is  so  little  hydrated  that  it  remains  a  prac- 
tically anhydrous,  leather-like  mass  in  all  the  tubes. 

In  order  not  to  lengthen  these  pages  unduly  with  protocols,  it 
may  suffice  merely  to  state  that  findings  entirely  similar  to  those 
just  described  are  obtainable  with  the  neutral  salts  of  the  soluble 
sulphates. 


216 


SOAPS  AND  PROTEINS 


FIGURE  104. 


FIGURE  105. 


FIGURE  106. 


FIGURE  107. 


FIGURE  108. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES 


217 


TABLE   LXVIII 

EGG-GLOBULIN  AND  CHLORIDS 


Control 
HjO. 

Salt. 

Final  concentration  of  the  salt  in  the  system. 

1/45  m 

1/40  m 

1/35  m 

1/30  m 

1/25  m 

White  curdy 
precipitate 

KC1 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

NaCl 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

MgCh 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

CaCli 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

HgCh 

Tough  white 
curdy  pre- 
cipitate 

Tough  white 
curdy  pre- 
cipitate 

Tough  white 
curdy  pre- 
cipitate 

Tough  white 
curdy  pre- 
cipitate 

Tough  white 
curdy  pre- 
cipitate 

Tube  number  

1 

2 

3 

4 

5 

Control 
H20. 

Salt. 

Final  concentration  of  the  salt  in  the  system. 

1/20  m 

1/15  m 

1/10  m 

1/5  m 

1/1  m 

White  curdy 
precipitate 

KC1 

Partially 
hydrated 

Partially 
hydrated 

Partially 
hydrated 

Transparent 
gel 

Transparent 
gel 

White  curdy 
precipitate 

NaCl 

White  curdy 
precipitate 

Partially 
hydrated 

Partially 
hydrated 

Partially 
hydrated 

Transparent 
gel 

White  curdy 
precipitate 

MgClt 

White  curdy 
precipitate 

White  curdy 
precipitate 

White  curdy 
precipitate 

Milky  gel 

Transparent 
gel 

White  curdy 
precipitate 

CaCh 

White  curdy 
precipitate 

Partially 
hydrated 
white  mass 

Partially 
hydrated 
white  mass 

Partially 
hydrated 
white  mass 

Partially 
hydrated 
white  mass 

White  curdy 
precipitate 

HgCh 

Tough  white 
curdy  pre- 
cipitate 

Tough 
slightly 
hydrated 
white  mass 

Tough 
slightly 
hydrated 
white  mass 

Leathery 
white 
mass 

Leathery 
white 
mass 

Tube  num 

ber  

6 

7 

8 

9 

10 

218  SOAPS  AND  PROTEINS 

4.  The  System  Gelatin/Water 

We  shall  now  consider  a  "  neutral "  protein  which,  when  com- 
pared with  the  fatty  acids,  is  not  "  insoluble  "  in  water  (as  glob- 
uHn)  but  "  soluble,"  namely  gelatin.  The  ordinary  alleged  acid- 
and  base-free  gelatin  1  will,  by  itself,  with  water,  show  all  the  four 
types  of  hydrophilic  colloid  systems  described  for  the  soaps.2 

Dry  gelatin  absorbs  water  (to  yield  the  system  water-dissolved- 
in-gelatin)  and  has  a  limited  solubility  in  water  (to  yield  the  system 
gelatin-dissolved-in-water).  Between  these  extremes  and  depend- 
ing merely  upon  the  relative  amounts  of  gelatin  and  water  present 
there  lie  the  systems  gelatin-solution  dispersed  in  hydrated-gelatin 
(gel)  or,  with  more  water,  hydrated-gelatin  dispersed  in  gelatin- 
solution  (sol). 

What  is  the  action  of  alkalies  (or  acids)  upon  these  systems? 

Under  variously  worded  headings  this  problem  has  received 
much  study.  The  effects  of  alkalies  (and  acids)  upon  the  lower- 
most of  the  four  systems  may  be  found  described  under  the  cap- 
tion "  swelling  "  of  gelatin  in  the  presence  of  acids  and  alkalies;3 
their  effects  upon  the  system  gelatin-solution-in-hydrated-gelatin 
under  the  heading  liquefaction  and  "  solution  "  of  gelatin;4  their 
effects  upon  the  system  hydrated-gelatin-in-gelatin-solution  under 
studies  in  viscosity;5  their  effects  upon  the  system  true  solution 
of  gelatin-in-water  as  studies  on  the  "  solubility  "  of  gelatin.6 
What  is  the  relationship  between  all  these? 

It  is  well  to  begin  by  inquiring  into  the  relationship  between 
the  swelling  of  a  "  soluble  "  "  neutral  "  protein  and  its  "  solution." 

1  See  the  footnote  on  page  209. 

2  See  page  69. 

8  See  for  example  K.  SPIRO:  Hofmeister's  Beitrage,  5,  276  (1904);  WOLF- 
GANG OSTWALD:  Pfliiger's  Arch.,  108,  563  (1905);  MARTIN  H.  FISCHER: 
(Edema  and  Nephritis,  3rd  Ed.,  75,  New  York  (1920)  where  references  to 
the  earlier  studies  may  be  found. 

4  MARTIN  H.  FISCHER:  Science,  42,  223  (1915);  Kolloid-Zeitschr.,  17,  1 
(1915). 

6  See  for  example  the  work  of  HOFMEISTER,  PAULI,  HARDY,  VON 
SCHROEDER,  HANDOVSKY,  SCHORR,  etc.,  on  the  viscosity  of  liquid  proteins 
("sols"). 

6  MARTIN  H.  FISCHER:  (Edema  and  Nephritis,  3rd  Ed.,  513,  New  York 
(1920).  As  of  similar  import  but  upon  other  proteins  may  be  cited  some 
studies  on  wheat  gluten.  T.  B.  WOOD  and  W.  B.  HARDY  (Proc.  Roy.  Soc., 
London,  Series  B,  81,  38  (1908))  studied  the  "disintegration"  and  "solu- 
tion" of  gluten  under  the  influence  of  acids  while  F.  W.  UPSON  and  J.  W. 
CALVIN  (Jour.  Am.  Chem.  Soc.,  37,  1295  (1915))  studied  its  swelling  under 
similar  circumstances. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  219 

The  notion  that  solution  is  but  a  contin- 
uation of  swelb'ng  persists  to  this  day.1 
Investigation  2  of  the  problem,  however, 
has  shown  that  this  is  not  the  case.  The 
matter  is  easily  proved  by  working  with 
gelatin  at  concentrations  and  tempera- 
tures near  its  gelation  or  melting  point. 
Since  alkalies  and  acids  increase  hydra- 
tion  (increase  swelling)  the  addition  of 
these  substances  to  a  barely  liquid 
gelatin-water  mixture  ought  to  stiffen  it. 
As  a  matter  of  fact  just  the  reverse  occurs. 
By  working  with  a  stiff  gelatin,  a  pre- 
viously solid  mixture  is  made  to  liquefy 
upon  the  addition  of  these  substances. 

The  phenomena  of  swelling  (hydratiori) 
and  of  "  solution  "  3  in  such  soluble  protein 
gels  as  gelatin,  while  frequently  associatedj 
are  therefore  essentially  different.  Swelling 
is  best  understood  as  a  change  whereby  the 
protein  enters  into  physico-chemical  com- 
bination with  more  of  the  solvent  (water),  as 
a  change  in  the  direction  of  greater  solubility 
of  the  solvent  in  the  protein;  "  solution  " 
is  best  conceived  of  as  a  change  in  the  direc- 
tion of  greater  solubility  (an  increased  degree 
of  dispersion)  of  the  colloid  in  the  solvent. 
If  reference  is  made  to  Figs.  48  and  49 
(page  70)  it  will  be  noted  that  changes 
involving  swelling  occur  in  the  region 
below  the  level  marked  V;  changes  in 
the  direction  of  liquefaction  or  "  solu- 
tion "  above  the  level  marked  F.  A 

1  See  for  example  WOLFGANG  PAULI  :  Kolloidchemie  der  Eiweisskorper, 
63,  Dresden  (1920). 

2  MARTIN  H.  FISCHER:   Science,  42,  223  (1915);   Kolloid-Zeitschr.,  17,  1 
(1915). 

3  Since  there  are  many  opinions  regarding  the  nature  of  "solution,"  accu- 
rate definition  of  the  term  is  not  easy.     We  are  here  using  the  term  in  its 
broadest  sense  as  covering  everything,  in  the  case  of  the  colloids,  from  their 
liquefaction  point  upwards  to  the  accepted  "true"  solution  of  the  physical 
chemists. 


220 


SOAPS  AND  PROTEINS 


single   experiment,  chosen  from  many,  may  serve    to  illustrate 
the  point. 

In  Table  LXIX  and  Fig.  109  is  shown  how  the  addition  of  a 
fixed  alkali  to  an  otherwise  solid  gelatin  gel  liquefies  this. 


TABLE   LXIX 

NEUTRAL  GELATIN  GEL  AND  ALKALI 


Tube 
number. 

Concentration  of  mixture. 

1 

2  cc.  10  percent 

gelatin  +  8  cc.  HzO 

2 

2  cc.  10 

"      +0.1  cc.  n/10 

NaOH  +  7.9cc. 

HzO 

3 

2  cc.  10 

"      +0.2cc.      ' 

"      +7.8cc. 

" 

4 

2  cc.  10 

"      +0.3cc.      " 

"      +7.7cc. 

" 

5 

2  co.  10 

"      +0.4cc.     " 

"      +7.6cc. 

44 

6 

2  cc.  10 

"      +0.5cc.      " 

"      +7.5cc. 

1  • 

7 

2  cc.  10 

"      +1.0cc.      " 

"      +7.0cc. 

" 

8 

2  cc.  10 

+  1.5cc.      " 

"      +6.5cc. 

1  ' 

9 

2  cc.  10 

"      +2.0cc.      " 

"      +6.0cc. 

1  ' 

10 

2  cc.  10        '  ' 

"      +2.5cc.     " 

"      +5.5cc. 

'  ' 

11 

2  cc.  10        '  ' 

"      +3.0cc.     " 

+  5.0  cc. 

The  mixtures  were  liquefied  in  a  warm-water  bath.  After  standing  for  twenty-four 
hours  at  25°  C.  the  gelatin  in  tube  1  was  solid;  that  in  tubes  2,  3,  4  and  5  was  also  solid; 
in  tube  6  the  surface  quivered  on  shaking.  The  gelatin  in  tube  7  flowed  as  a  viscid  liquid. 
In  the  remaining  tubes  the  gelatin  was  entirely  liquid. 

TABLE   LXX 
NEUTRAL  GELATIN  GEL  AND  ACID 


Tube 
number. 

Concentration 

of  mixture. 

1 

2  cc.  10  percent  gelatin  +8  cc.  HjO 

2 

2cc.  10        " 

+0.  1  cc.  n/10  HC1  +  7.9  cc. 

HiO 

3 

2  cc.  10        " 

"      +0.2cc.     " 

'    +7.8cc. 

44 

4 

2  cc.  10        '  ' 

"      +0.3cc.     " 

1    +7.7cc. 

44 

5 

2  cc.  10        '  ' 

"      +0.4cc.     ". 

'    +7.  6  co. 

44 

6 

2  cc.  10        " 

"      +0.5cc.     " 

'    +7.5cc. 

44 

7 

2  cc.  10        '  ' 

"      +1.0cc.     " 

'    +7.0cc. 

44 

8 

2  cc.  10 

"      +1.5cc.      " 

1    +6.5cc. 

" 

9 

2  cc.  10 

"      +2.0cc.      " 

'    +6.0cc. 

" 

10 

2  cc.  10 

"      +2.5cc.     " 

'    +5.5  cc. 

" 

11 

2  cc.  10 

"      +3.0  cc.  .  " 

'    +5.0cc. 

After  these  mixtures  had  stood  for  twenty-four  hours  the  control  gelatin  in  tube  1 
was  perfectly  solid.  The  mixtures  in  tubes  2,  3,  4,  5  and  6  were  so  solid  that  they  could 
be  turned  over,  though  on  hard  shaking  they  quivered;  in  tube  7  the  gelatin  flowed  as 
a  viscid  liquid;  in  tubes  8,  9,  10  and  11  the  mixtures  were  entirely  fluid. 

Table  LXX  brings  out  the  same  general  truths  for  the  addition 
of  acid  to  an  otherwise  solid.  "  neutral  "  gelatin  gel. 

In  interpreting  the  findings  here  described  we  would  say  that 
under  the  influence  of  the  added  alkali  or  acid  the  "  neutral  " 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES 


221 


gelatin  is  converted  into  a  basic  gelatinate  or  a  gelatin  chlorid. 
These  compounds,  at  the  same  concentration,  are  more  soluble 
in  water  than  the  neutral  gelatin  and  hence  the  liquefaction  of 
these  systems. 

TABLE  LXXI 
SODIUM  GELATINATE  AND  SALT 


Tube 
number. 

Concentration  of  mixture. 

! 

2  cc. 

10 

percent  gelatin  +  8 

cc.  H2O 

2 

2  cc. 

10 

+1 

.5cc.  n/10 

NaOH+6.5  cc. 

HzO 

3 

2  cc. 

10 

"      +1 

.  5  cc.     " 

"      +0.1  cc. 

m  NaCl  +  6 

4  cc. 

H»O 

4 

2  cc. 

10 

"      +1 

.  5  cc.     " 

"      +0.2cc. 

"      "     +6 

3  cc. 

" 

5 

2  cc. 

10 

"      +1 

.5cc.     " 

"      +0.3cc. 

"       "     +6 

2  cc. 

«  « 

6 

2  cc. 

10 

"      +1 

.5cc.     " 

"      +0.4cc. 

"      "     +6 

1  cc. 

" 

7 

2  cc. 

10 

"      +1 

.  5  cc.     " 

"      +0.5cc. 

"      "     +6 

0  cc. 

•  • 

8 

2  cc. 

10 

"      +1 

.  5  cc. 

"      +1.0  cc. 

"      "     +5 

5  cc. 

•  • 

9 

2  cc. 

10 

"      +1 

.5cc.      " 

"      +2.0cc. 

"      "     +4 

5cc. 

1  • 

10 

2  cc. 

10 

"      +1 

.  5  cc.     " 

"      +3.0cc. 

"      "     +3 

5  cc. 

1  ' 

11 

2  cc. 

10 

+  1 

.  5  cc.     " 

"      +4.0cc. 

„      ..     +2 

5  cc. 

1  ' 

12 

2  cc. 

10 

"      +1 

.  5  cc.     " 

"      +5.0cc. 

+  1 

5  cc. 

At  the  end  of  twenty-four  hours  the  pure  gelatin  was  solid;  the  gelatin  plus  the  alkali 
was  liquid.  The  tubes  containing  sodium  chlorid  in  addition  were  all  solid,  the  optimum 
stiffening  effect  of  the  salt  being  evident  in  tube  7. 

TABLE   LXXII 

GELATIN  CHLORID  AND  SALT 


Tube 
number. 

Concentration  of 

mixture. 

1 

2  cc.  10  percent 

gelatin  +  8  cc.  H2O 

2 

2cc.  10        " 

"      +1.5  cc.  n/10  HC1  +  6.5  cc. 

HiO 

3 

2  cc.  10        " 

"      +1.5cc.     " 

+0.1  cc. 

m  NaCl+6.4  cc. 

HzO 

4 

2  cc.  10        " 

"      +1.5cc.     " 

+0.2  cc. 

"      "     +6.3cc. 

" 

5 

2  cc.  10        " 

"      +1.5cc.     " 

+0.3  cc. 

"      "     +6.2cc. 

11 

6 

2  cc.  10        " 

"         +1.0CC.        " 

+0.4  cc. 

"      "     +6.  Ice. 

" 

7 

2  cc.  10 

"      +1.5cc.      " 

+0.5  cc. 

"      "     +6.0cc. 

•« 

8 

2  cc.  10 

"      +1.5cc.      " 

+  1  .  0  cc. 

"      "     +5.5cc. 

•• 

9 

2  cc.  10 

"       +1.5cc.      " 

+2.0cc. 

"      "     +4.5cc. 

•• 

10 

2  cc.  10        " 

"      +1.5cc.      " 

+3.0  cc. 

"      "     +3.5cc. 

" 

11 

2  cc.  10        " 

"      +1.5cc.      " 

+4.0  cc. 

"      "     +2.5CC. 

" 

12 

2  cc.  10        " 

'  '      +  1  .  5  cc.      " 

+  5.0  cc. 

"      "     +  1  .  5  cc. 

Twenty-four  hours  after  the  mixtures  had  been  prepared  the  pure  gelatin  in  tube  1 
was  solid;  the  acidified  gelatin  in  tube  2  was  liquid.  A  distinct  influence  of  the  sodium 
chlorid  was  evident  even  in  tube  3  where  the  mixture  barely  flowed.  The  viscosity  increased 
progressively  from  tube  4  to  tube  7  in  which  the  optimum  effect  of  the  sodium  chlorid  was 
observed.  Here  the  gelatin  was  solid,  but  not  quite  so  solid  as  the  pure  gelatin.  The 
gelatin  mixtures  in  tubes  8,  9,  10,  11  and  12  were  solid,  but,  on  being  tapped,  quivered 
more  easily  than  did  the  gelatin  in  tube  7. 


222  SOAPS  AND  PROTEINS 

To  illustrate,  now,  upon  such  basic  (or  acidic)  gelatin  the 
effects  of  a  neutral  salt  (in  mimicry  of  the  salting-out  effects 
observed  upon  soaps),  Tables  LXXI  and  LXXII  are  introduced. 
They  show  that  the  addition  of  a  neutral  salt  in  increasing  con- 
centration to  a  previously  liquid  gelatin  at  first  increases  its  viscosity 
to  an  optimum  point  (gelation)  and  then  decreases  it.  The  same 
explanation  holds  for  this  finding  as  in  the  case  of  the  soaps.  The 
salt  becomes  hydrated  and,  as  salt-water,  becomes  emulsified  in 
the  hydrated  basic  (or  acidic)  gelatin.  With  salt  added  beyond  the 
optimum  point  the  salt-water  becomes  the  external  phase  and  the 
viscosity  of  the  system  falls.  With  enough  salt  added  the  whole 
of  the  gelatin  (as  sodium  gelatinate  or  gelatin  chlorid  and  not  as 
"  neutral  "  gelatin)  separates  off  in  practically  anhydrous  form. 

5.  Supplementary  and  Critical  Remarks 

§1 

It  is  necessary  to  keep  clearly  in  mind  that  the  possibilities  for 
chemical  and  colloid-chemical  change  as  thus  far  outlined  for  the 
fatty  acids  and  the  proteins  constitute  only  a  small  fraction  of 
those  which  may  be  induced. 

While  we  have  said  that  only  alkalies  will  unite  with  the  fatty 
acids  and  only  alkalies  and  acids  (or  their  salts)  with  the  poly- 
merized amino-acids  called  proteins,  the  former  may  be  sulphon- 
ated,  may  be  saturated  with  hydrogen,  may  be  oxidized  or  iodized 
while  the  latter  may  also  be  oxidized,  hydroxylated  or  have  acids 
bound  to  them  elsewhere  in  the  molecule  than  at  an  NH2  grouping. 
As  each  of  these  chemical  changes  is  induced  the  fatty  acid  derivative 
or  the  protein  derivative  assumes  new  properties  of  solubility  for 
water  and  in  water  and  as  this  happens  the  colloid-chemical  prop- 
erties (like  the  viscosity)  of  the  system  in  which  such  a  chemical 
change  has  been  induced,  must  also  change.1 

To  keep  things  simple  we  have  also  touched  upon  only  the 
grosser  of  the  phase  differences  present  as  neutral  proteins  unite 
with  alkalies  or  acids.  How  much  more  complicated  in  fact  are 
the  systems  which  have  been  described  is  apparent  when  reference 
is  made  to  Figs.  48  and  49  and  the  system,  stearic  acid/alkali/ 

1  The  derivatives  listed  have  already  been  partly  studied  in  our  laboratory 
and  will  be  reported  upon  later. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  223 

water  is  considered  and  compared  with  the  analogous  system 
protein/alkali/water. 1 

If  neutralization  is  not  complete,  the  result  is  an  emulsion  of 
the  uncombined  fatty  or  proteinic  acid  in  such  hydrated  "  soap  " 
as  is  produced.  If  neutralization  is  complete  and  the  water  con- 
tent is  sufficiently  low,  only  pure  hydrated  alkali  stearate  or 
hydrated  alkali  proteinate  is  obtained.  This  obviously  corre- 
sponds to  the  lowermost  levels  of  the  two  diagrams.  Depend- 
ing upon  the  temperature  either  solid  (Fig.  49)  or  liquid  (Fig.  48) 
systems  may  be  obtained.  With  sufficient  water,  only  a  true 
"  solution  "  of  the  alkali  stearate  or  alkali  proteinate  in  water  is 
obtained.  We  are  then  in  the  topmost  levels  of  the  two  diagrams. 
In  such  solution,  however,  there  follows  hydrolysis  of  these  com- 
pounds, so  that  in  addition  to  molecules  in  solution  there  may 
appear,  beside  the  soap,  free  fatty  or  proteinic  acid  and  free 
alkali  and  along  with  these  the  ions  of  these  substances.  The 
presence  of  such  ions  in  the  case  of  protein/water  systems  has 
commonly  been  called  upon  to  account  for  their  colloid-chemical 
properties.  Things  are  almost  exactly  the  reverse.  The  most 
definitely  colloid  soap  or  protein/water  systems,  in  other  words 
the  more  concentrated  ones,  are  at  the  other  end  of  the  diagrams 
and  show  no  ions  at  all.  Whenever  such  appear,  they  are  the 
accidental  products  of  dilution  and  hydrolysis.  They  begin  to 
appear  therefore  as  soon  as  soap  or  protein  in  true  solution  in 
water  appears  within  the  hydrated  soap  or  protein,  in  other  words 
in  all  the  various  mixed  systems  which  lie  in  or  above  the  level  Y. 
The  ions  are,  however,  not  in  the  hydrated  colloid,  but  in  those 
portions  of  these  mixed  systems  which  contain  dissolved,  dissoci- 
ated and  hydrolyzed  soap  or  protein. 

To  illustrate  the  infinite  variety  of  systems  that  may  result 
from  mixture  of  a  base  with  a  fatty  acid  or  protein  we  need  but 
list  the  following:  fatty  or  proteinic  acid  emulsified  in  hydrated 
soap  or  basic  proteinate,  and  vice  versa;  soap  or  protein  "  solu- 
tion "  in  solid  hydrated  soap  or  basic  proteinate,  and  vice  versa; 
soap  or  protein  "  solution  "  in  liquid  hydrated  soap  or  basic  pro- 
teinate and  vice  versa;  soap  or  protein  "  solution/'  pure  and  free 
from  ions  or  such  as  contains  free  fatty  or  proteinic  acid,  free 
alkali,  and  the  whole  gamut  of  ions; — all  determined  obviously 

1  Figs.  13  and  76  and  Figs.  98  to  103  with  the  accompanying  texts 
should  be  studied  in  this  connection. 


224  SOAPS  AND  PROTEINS 

by  the  concentrations  of  the  various  materials  existing  in  any  sys- 
tem, by  the  content  of  water  in  the  system  and  the  temperature. 
Every  one  of  these  systems  may  be  produced  at  will  from 
fatty  acids  and  alkali  or  from  "  neutral  "  proteins  with  alkali 
or  acid. 

§2 

It  will  be  noticed  that  the  above  remarks  attempting  to 
explain  the  colloid-chemistry  of  protein/ water  systems  have 
called  for  no  concepts  outside  those  of  mutual  solubility  and 
mutual  emulsification  or  suspension,  just  as  in  the  case  of  soap/ 
water  systems.  What  then  becomes  of  the  chemical,  electrical, 
surface  tension,  adsorption,  etc.,  theories  of  stability  in  colloid 
systems  proposed  by  various  authors?  The  answer  is,  we  think, 
simple.  Their  views  are  not  always  wrong,  but  they  suffer 
universally  from  one-sidedness.  They  err  either  because  they 
are  inadequate  to  explain  more  than  a  part  of  the  behavior  of 
all  colloid  systems  or  because  the  explanation  holds  for  only 
limited  examples.  If  reference  is  again  made  to  Figs.  48  and  49 
it  will  be  seen  that  those  authors,  for  example,  who  try  to  see 
in  all  colloid  systems  nothing  but  special  instances  of  modified 
"  true  solutions  "  are  clearly  trying  to  find  the  explanation  of 
all  colloid  phenomena  in  regions  lying  above  the  level  E,  and 
that  often  they  are  attempting  to  do  this  by  the  changes  incident 
to  mere  passage  from  some  one  horizontal  level  to  the  next.  Such 
a  view  is  obviously  too  limited,  for  it  ignores  the  behavior  of  all 
such  systems  as  lie  below  the  level  V.  Those  authors,  on  the 
other  hand,  who  hold  that  change  in  some  one  factor  is  responsible 
for  the  changes  in  stability  of  all  colloid  systems  suffer  from  a 
similar  limitation  in  point  of  view.  It  is  difficult,  for  example, 
to  conjure  up  electrical  notions  to  explain  the  stability  of  colloid 
systems  which  consist  merely  of  organic  solvents  and  materials 
like  fat  or  rubber.  Stoichiometrical  relationships  lose  their  force 
when  stabile  colloid  systems  can  be  built  of  most  variable  pro- 
portions of  fat  and  a  hydratable  carbohydrate  (for  example 
cottonseed  oil  in  hydrated  acacia,  glycogen  or  dextrin).  Sur- 
face tension  views  are  inadequate  when,  with  progressive  change 
in  surface  tension  relationship  between  any  two  substances,  stabil- 
ization is  obtainable  only  through  a  portion  of  the  range,  or,  con- 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  225 

versely,  throughout  the  whole  range  no  matter  what  the  surface 
values. 

And  yet  these  remarks  must  not  be  misunderstood.  They 
do  not,  in  the  first  place,  diminish  the  value  of  the  actual  observa- 
tions made  by  these  different  authors  upon  various  colloid  systems; 
nor  do  they  deny  that  the  factors  they  cite  are  not  of  some  impor- 
tance in  some  systems.  The  whole  problem,  obviously,  moves 
back  to  an  inquiry  into  still  more  fundamental  ones:  what  is 
the  nature  of  solution;  what  are  the  forces  active  in  producing 
and  maintaining  emulsions;  and  what  is  the  nature  of  solidifi- 
cation without  or  with  a  "  solvent  "? 

We  do  not  ourselves  presume  to  answer  these  questions.  In 
the  matter  of  the  nature  of  solution,  however,  we  would  like  to 
emphasize  our  growing  opinion  that  it  is  much  more  often  union 
in  quantitative  relations  between  dissolved  substance  and  the 
dissolving  medium  with  the  production  of  new  compounds  than 
is  at  present  accepted  by  the  "  dilute  solution  "  chemists;  and 
that,  especially  in  "  concentrated  "  systems,  this  factor  becomes  so 
great  that  the  added  element  of  mere  subdivision  of  one  material 
in  a  second,  so  heavily  stressed  in  the  "  dilute  "  solutions,  largely 
disappears. 

The  forces  active  in  stabilizing  a  colloid  system  may  be  any 
or  all  of  those  which  make  possible  or  give  character  to  a  "  solu- 
tion," or  which  permit  of  the  stabilization  of  one  material  in  a 
second  to  yield  either  (depending  upon  the  physical  state  of  the 
phases)  an  emulsion  or  a  suspension.  As  all  the  facts  of  mutual 
solution  cannot  be  understood  upon  any  purely  electrical  basis, 
and  as  all  the  phenomena  of  cohesion,  adhesion,  suspension, 
stabilization,  etc.,  cannot  at  present  be  understood  through  any 
single  notion  of  viscosity,  surface  tension  or  other  force,  neither 
can  purely  chemical,  purely  electrical  or  purely  surface  tension 
concepts  alone  "  explain  "  the  behavior  of  these  systems. 

6.  On  Peptization  and  Coagulation 

§1 

With  the  ideas  of  the  preceding  pages  in  mind  we  wish  now 
to  consider  certain  group  reactions  characteristic  of  different 
proteins,  to  see  if  some  simpler  concepts  than  we  now  possess 


226  SOAPS  AND  PROTEINS 

regarding  the  fundamental  nature  of  these  group  reactions,  can 
not  be  discovered.  Reference  is  made  to  their  "  peptization  " 
and  to  their  "  coagulation  "  under  various  circumstances  and 
to  the  colloid-chemical  equivalents  in  types  of  change  encountered 
in  the  physiology  and  pathology  of  protoplasm  under  the  terms 
liquefaction,  coagulation  and  necrosis. 

The  term  "  peptization  "  may  be  taken  for  our  purposes  as 
the  antonym  of  "  coagulation."  The  latter  term  has  been  applied 
to  what  represents  at  least  several  different  types  of  change  in 
protein/water  systems.  What  these  have  in  common,  however, 
is  a  change  in  state  from  one  in  which  the  protein  (or  soap)  is  in 
solution  or  suspension,  to  one  in  which  it  is  aggregated,  separated- 
out  or  precipitated.  In  the  terms  of  WOLFGANG  OSTWALD  the 
changes  characteristic  of  coagulation  are  essentially  those  of 
decrease  in  degree  of  dispersion,  in  other  words  changes  in  the 
direction  of  coarser  division  of  the  materials.  Associated  with 
such  a  change  may  be  one  in  water-holding  power,  in  optical 
properties,  in  viscosity,  etc.  There  are  those  who  would  restrict 
the  term  "  coagulation  "  to  such  changes  as  prove  irreversible. 
An  albumin  would  therefore  be  said  to  be  coagulable  through 
heat  or  a  mercury  salt  (since  lowering  of  temperature  or  dilution 
of  the  mercury  salt  does  not  bring  back  the  albumin  to  its  former 
"  dissolved  "  state);  it  would  not  be  coagulable,  however,  through 
saturated  magnesium  sulphate  solution  (for  this  on  dilution  allows 
the  "  albumin  "  to  resume  its  former  state).  In  the  latter  instance 
the  change  is  often  designated  as  a  precipitation  or  "  salting-out  " 
of  the  "  albumin."  It  does  not  matter,  for  our  purposes,  how 
the  terms  are  used,  for  colloid-chemistry  needs  to  consider  them 
all.  The  distinctions  are,  moreover,  arbitrary  for,  as  long  known, 
even  heat  coagulations  are  not  completely  irreversible  if  the  high 
temperature  is  not  maintained  too  long;  and  we  shall  see  later 
that,  just  as  in  the  case  of  the  soaps,  the  heavy  metal  coagula- 
tions of  the  proteins  can  also  be  "redissolved."  What  light  do 
the  observations  on  soaps  and  the  soap-like  protein  compounds 
already  described  cast  upon  the  nature  of  these  coagulative 
changes? 

In  order  to  illustrate  how  we  think  the  views  developed  in 
the  preceding  pages  should  be  applied  for  a  better  understanding 
of  the  practises  of  "  peptization  "  and  "  coagulation  "  in  protein 
systems,  we  shall  cite  examples  illustrating  protein  change  (1) 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  227 

of  the  peptization  and  coagulation  type,  (2)  of  the  heat  coagulation 
type  and  (3)  of  the  physiological  coagulation  type. 


§2 

Peptization  may  be  discussed  by  reference  to  the  well-known 
changes  suffered  by  a  protein  "  insoluble  "  in  water,  such  as 
casein,  when  this  is  subjected  to  the  action  of  any  of  the  light 
metal  alkalies.  Casein,  like  any  of  the  pure  higher  fatty  acids 
(for  example  palmitic),  when  mixed  with  water  fails  "  to  dissolve." 
Expressed  in  the  terms  developed  in  connection  with  the  theory 
of  the  lyophilic  soap  colloids,1  the  casein  and  the  palmitic  acid  are 
neither  soluble  in  water  nor  yet  solvents  for  water.  When,  how- 
ever, an  alkali  (like  sodium  hydroxid)  is  added  to  either,  both 
become  "  soluble/'  In  the  case  of  the  fatty  acid  we  have  long 
said  that  the  change  is  coincident  with  transformation  from  fatty 
acid  to  a  soap;  in  the  case  of  casein  (and  similar  proteins)  however, 
we  have  more  commonly  said  that  it  is  "  soluble  "  "  in  alkaline 
solutions,"  that  it  is  "  peptized  "  by  alkalies,  that  it  "  becomes 
colloidally  dispersed  through  a  requisite  number  of  OH  ions," 
etc.  It  simplifies  matters  and  is  more  correct  to  say  that  what 
happens  is  the  same  in  both  sets  of  materials.  From  the  casein, 
too,  is  formed  a  soap-like  compound  (namely  sodium  caseinate) 
which  is  not  only  more  soluble  in  water  but  also  a  better  solvent 
for  water  than  the  original  "  neutral  "  casein.  As  the  soaps  are 
best  thought  of  as  definite  compounds,  each  with  its  own  solubility  in 
water  and  its  own  solvent  power  for  water,  so  also  is  it  best  to  conceive 
of  the  basic  and  metallic  proteinates  also  as  definite  chemical  com- 
pounds possessed  of  their  own  solubility  in  water  and  solvent  power 
for  water. 

The  idea  that  alkalies  (or  acids)  unite  with  protein  to  yield  new 
compounds  is,  by  itself,  of  course,  not  new.  It  was  early  expressed 
by  S.  BUGARSKY  and  L.  LIEBERMANN  2  and  has,  since  their  studies, 
been  confirmed  and  developed  by  W.  B. HARDY,3  WOLFGANG  PAULI,* 

1  See  page  64. 

2S.  BUGARSKY  and  L.  LIEBERMANN:  Pfliiger's  Arch.,  72,  51  (1898). 

3  W.  B.  HARDY:  Jour.  Physiol.,  33,  251  (1905). 

4  WOLFGANG  PAULI:  Kolloidchemie  der  Eiweisskorper,  69,  Dresden  (1920) 
where  may  be  found  the  references  to  his  earlier  studies. 


228  SOAPS  AND  PROTEINS 

E.  LACQUEUR,  0.  SACKUR/  L.  L.  VAN  SLYKE,2  A.  W.  BoswoRTH,3 
T.  B.  ROBERTSON,4  etc. 

The  difficulty  with  the  work  of  these  authors,  if  we  may  express 
an  opinion,  is  that  with  developmnt  to  quantitative  levels  of  their 
chemical  views  covering  such  protein/electrolyte/water  systems, 
they  have  seemed  constantly  to  support  the  expressed  or  implied 
view  that  with  the  pure  chemistry  of  these  systems  settled,  an 
understanding  of  their  colloid-chemical  behavior  followed  as  a 
self-evident  corollary. 

This  view  is,  we  think,  fundamentally  false.  While  union  in 
stoichiometrical  relations,  qualitative  and  quantitative  changes  in 
electrical  charge,  the  accepted  theories  of  "  dilute  solution,"  etc.,  may 
all  at  times  be  factors  appearing  in  a  colloid  system  and  may,  in  fact, 
in  part  determine  the  behavior  of  colloid  systems,  their  quantitative 
appraisement  is  in  no  instance  adequate  to  "  explain  "  the  colloid 
state.  The  colloid  properties  of  a  casein/sodium  hydroxid/water 
system  (ignoring  for  the  present  the  presence  of  an  overplus  of 
either  alkali  or  casein)  are  those  of  a  sodium  caseinate/water  sys- 
tem and  these,  depending  solely  upon  the  concentration  of  the 
water  in  the  system,  vary  from  the  extreme  of  a  gelatinous  solu- 
tion of  water  in  the  caseinate  on  the  one  hand  to  a  true  solution 
of  sodium  caseinate  in  water  on  the  other. 

It  is  well  to  emphasize  at  once  the  proper  significance  to  be 
given  the  electrical,  ionic,  viscosity,  etc.,  properties  which  such  a 
system  may  show.  In  the  presence  of  sufficiently  little  water  a 
chemically  neutral  sodium  caseinate  is  not  only  solidly  gelatinous 
but  also  neutral  to  an  indicator  like  phenolphthalein,  as  witness 
the  lower  section  of  the  test-tube  shown  in  Fig.  110.  While 
this  finding  is  commonly  interpreted  in  the  terms  of  orthodox 
physical  chemistry  as  proof  that  in  such  "  highly  concentrated 
solutions  "  (as  in  the  highly  concentrated  soaps),  there  is  no  ade- 
quate hydrolysis  and  electrolytic  dissociation  to  yield  an  overplus 
of  OH  ions,  we  ourselves  hold  that  it  is  just  as  correct  and  more 

1  E.  LACQUEUR  and  O.  SACKUR:  Hofmeister's  Beitr.,  3,  196  (1902). 

2  L.  L.  VAN  SLYKE  and  co-workers:    Am.  Chem.  Jour.,  33,  461  (1905); 
ibid.,  38,  393  (1907). 

3  A.  W.  BOSWORTH  and  L.  L.  VAN  SLYKE:  Jour.  Biol.  Chem.,  14,  203  (1913)  • 
ibid,  19,  67  (1914);  BOSWORTH:  ibid.,  20,  91  (1915). 

4T.  B.  ROBERTSON:  Jour.  Biol.  Chem.,  2,  317,  337  (1907);  ibid.,  5,  493 
(1909);  ibid,  8,  287  (1910);  Physical  Chemistry  of  the  Proteins,  85,  New 
York  (1918).  Here  references  to  the  older  literature  may  be  found. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES 


229 


r; 


reasonable  to  consider  this  proof  that  the  system  water-dis- 
solved-in-sodium-caseinate  is  something  different  from  a  solution 
of  sodium-caseinate-in- water.  It  must  be  admitted  either  (1)  that 
indicator  methods  may  not  be  applied  to  such  a  system  or  that  if 
they  are  applicable  (2)  it  contains  no  ions.  We  reemphasize  the 
point  because  to  our  minds  the  tissues  of  the  body,  including  the 
blood  and  lymph,  are  such  solutions  of  water 
in  protein  (protoplasm)  and  that,  like  a  con- 
centrated sodium  caseinate/water  system,  they 
are  electrically  neutral,  that  indicator  methods 
cannot  be  applied  to  them  without  the  greatest 
reserve  and  that  it  is  fundamentally  false  to 
regard  them  as  systems  for  which  the  laws  of 
the  ordinary  dilute  solutions  may  be  expected 
to  be  valid. 

Slight  dilution  of  the  concentrated  sodium 
caseinate/water  system  with  water  suffices  to  turn 
it  pink  even  when  the  system  is  still  entirely  solid. 
What  turns  pink  is  that  portion  of  the  emulsion 
thus  formed  which  represents  the  phase,  dilute 
solution  of  sodium  caseinate  in  water  subdivided 
in  the  unchanged  (more  solid)  solution  of  water 
in  sodium  caseinate. 

Still  further  dilution  increases  the  amount  of 
the  dilute  solution  phase  and  therefore  the  inten- 
sity of  the  pink  color  (see  Fig.  110).  When 
sufficient  water  is  added  the  system  becomes 
more  liquid  since  it  is  now  composed  of  a  subdi- 
vision of  hydrated  sodium  caseinate  particles 
within  a  "  true  "  solution  of  sodium  caseinate  as 
an  external,  enveloping  phase. 

On  extreme  dilution  the  system  becomes  in- 
tensely   red    (see   the  upper  sections  of    the  tube  in  Fig.  110) 
because  this  is  merely  a  dilute  solution  of  sodium  caseinate  in 
water  which  has  at  the  same  time  suffered  great  hydrolysis. 

Just  as  the  solubility  and  hydration  properties  of  any  fatty 
acid  with  different  bases  change  as  we  pass  from  the  alkali  metals 
through  the  alkaline  earths  to  the  heavy  metals,  so  also  do  the 
solubility  and  hydration  capacities  of  casein,  and  in  the  same 
general  fashion.  The  changes  observed  in  the  system  as  one 


FIGURE  110. 


230  SOAPS  AND  PROTEINS 

metal  displaces  another  explain  much  of  what  is  ordinarily 
described  under  the  head  of  the  "  peptization,"  "  precipitation  " 
or  "  coagulation  "  of  the  protein  colloids. 

When  potassium  hydroxid,  for  example,  is  added  to  a  sodium 
caseinate/ water  system  it  is  "  peptized  "  and  becomes  more 
liquid;  while  through  the  addition  of  magnesium,  calcium  or  iron 
salts  precipitation  or  "  coagulation  "  is  produced.  We  prefer  to 
say  that  in  the  first  instance  materials  are  formed  (potassium 
caseinate)  which  are  more  soluble  in  water,  wherefore  the  whole 
system  tends  in  the  direction  of  the  less  viscid  true  solution; 
while  in  the  second,  materials  are  produced  which  are  less  soluble 
in  water  and  are  possessed  of  a  lower  hydration  capacity.  Hence 
their  separation  from  the  dispersion  medium. 

As  reversion  from  a  state  of  low  hydration,  low  solubility  and 
precipitation  to  a  state  of  higher  hydration  and  "  solution  "  is  most 
easily  obtained  in  the  case  of  the  soaps  when  the  alkali  metals  are 
involved,  is  more  difficult  when  those  of  the  alkaline  earths  are 
considered  and  is  generally  said  to  be  impossible  in  the  case  of  the 
heavy  metal  soaps,  so  also  in  the  case  of  the  proteins  are  the  similar 
reversions  accomplished  with  increasing  difficulty  and  more  and 
more  slowly  as  we  pass  from  the  alkalies  through  the  alkaline 
earths  to  the  heavy  metals.  The  heavy  metal  salts  are  for  this 
reason  regularly  listed  as  "  coagulants  "  of  the  proteins,  while 
those  of  the  alkaline  earths  occupy  an  ambiguous  middle  ground. 
The  light  metal  salts  act  merely  as  "  precipitants  "  for  the  proteins. 
As  previously  emphasized  1  and  to  be  touched  upon  again  2  these 
facts  are  of  importance  not  only  for  the  understanding  of  the 
nature  of  certain  coagulations  but  embody  the  principles  which 
must  be  employed  when  such  coagulations  appear  in  living  matter 
in  consequence  of  heavy  metal  poisoning. 


§3 

It  is  necessary  now  to  discuss  the  effects  of  temperature  upon 
the  proteins,  associated  with  which  is  the  question  of  their  heat 
coagulation  in  order  to  see  where  this  set  of  phenomena  has  its 
analog  in  the  colloid-chemistry  of  the  soaps. 

1  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:  Science,  43,  469  (1918). 

2  See  page  240. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  231 

For  a  few  of  the  proteins  (as  gelatin)  in  the  presence  of  the  light 
metal  bases,  the  effects  of  temperature  may  be  dismissed  with  the 
statement  that  raising  the  temperature  merely  moves  the  system 
in  the  direction  of  true  solution  in  water.  As  ordinarily  stated, 
the  proteins  are  "  more  soluble  "  at  the  higher  temperatures  and 
are  "  not  coagulable  "  by  heat.  The  same  might,  of  course,  be 
said  of  the  "  solubility  "  of  the  lower  fatty  acids  when  these,  in 
the  presence  of  sodium  or  potassium  hydroxid  and  water  are  raised 
in  temperature.  When  the  same  proteins  are  examined  in  the 
presence  of  magnesium  or  calcium  their  behavior  becomes  "ambig- 
uous," while  in  the  the  presence  of  heavy  metals  the  proteins  are 
uniformly  coagulable  at  all  temperatures.  The  reasons  for  this 
are  to  be  found  in  the  fact  that  many  of  the  magnesium  and 
calcium  proteinates  (like  the  magnesium  and  calcium  soaps)  are 
little  more  "  soluble  "  at  higher  temperatures  than  at  lower  ones, 
while  all  the  heavy  metal  proteinates,  like  the  heavy  metal  soaps, 
have  a  low  hydration  capacity  and  a  low  solubility  in  water  at  all 
temperatures. 

The  accepted  example  of  heat  coagulation  (or  heat  denaturiza- 
tion  of  the  "  protein  ")  is,  however,  best  seen  in  certain  of  the  pro- 
teins like  various  albumins  and  globulins.  Here  rise  in  temperature 
even  in  the  presence  of  light  metals  does  not  favor  hydration  and 
solution  of  the  "  protein  "  but  just  the  reverse.  Where  in  the 
colloid-chemistry  of  the  soaps  do  we  encounter  an  analogous  set  of 
facts?  Nowhere  in  the  group  of  the  systems  composed  of  pure  soaps 
and  little  water,  but  in  the  behavior  of  those  in  which  through  hydroly- 
sis or  otherwise  the  separation  of  insoluble  free  fatty  add  is  favored. 
In  the  case  of  the  "heat  coagulable  "  proteins  it  is  also  a  matter,  not  of 
the  coagulation  of  the  potassium,  sodium,  etc.,  proteinates  through 
increase  in  temperature  but  of  the  free  (proteinic)  acid  formed  after 
hydrolysis.  The  items  which  favor  such  heat  coagulation  are  the 
items  which  make  for  increase  in  hydrolysis  or  displacement  of  the 
system  in  the  direction  of  a  higher  concentration  of  free  proteinic 
acid.  The  heat  itself  does  this,  though  the  whole  process  is 
favored  by  dilution  of  the  system  with  water,  and  the  addition 
of  small  amounts  of  acid.  Heat-coagulated  protein/water  systems 
are  considered  as  among  the  most  typical  of  the  irreversible 
coagulations.  Reversible,  however,  they  are,  as  witness  their 
swelling  and  solution  when  such  "  denatured  "  proteins  are  treated 
with  light  metal  hydroxids.  The  same  phenomena  are  observable 


232  SOAPS  AND  PROTEINS 

in  the  soaps.  On  dilution  and  application  of  heat  the  light  metal 
soaps,  especially  of  the  higher  fatty  acids,  suffer  great  hydrolysis, 
and  this  hydrolysis  is  not  reversible  on  simple  lowering  of  tem- 
perature. But  let  the  freed  fatty  acid  be  treated  with  more  con- 
centrated alkali,  and  reversion  to  a  "  swelling  and  soluble  fatty 
acid  " — to  speak  for  the  moment  in  the  terms  of  protein  chemis- 
try— gradually  comes  about. 

In  a  careful  study  of  this  problem  KRAFFT  J  boiled  a  unit 
weight  (1  gram)  of  soap  (sodium  palmitate)  with  increasing  vol- 
umes (200  to  900  cc.)  of  water.  Just  as  when  certain  protein 
"  solutions  "  are  thus  boiled,  these  soap  mixtures  become  milky. 
On  cooling,  a  shining  precipitate  settles  out  which  on  analysis 
shows  a  progressively  lower  percentage  of  sodium  and  higher  per- 
centage of  fatty  acid  when  compared  with  the  composition  of  the 
pure  soap,  as  the  volume  of  water  in  which  the  soap  was  boiled  is 
increased.  The  original  soap  contained  8.27  percent  sodium. 
In  contrast  to  this  the  cooled  fraction  when  boiled  with  200  cc. 
water  showed  but  7.01  percent;  with  450  cc.  water,  6.32  percent; 
with  900  cc.  water,  4.20  percent.  KRAFFT  interpreted  this  finding 
as  indicating  that  there  was  a  splitting  of  the  soap  into  sodium 
hydroxid  and  "  acid-soap  "  (sodium  bipalmitate).  This  idea  has 
since  been  frequently  adopted  by  other  workers.  It  is,  to  our 
minds,  only  partly  correct.  There  is,  undoubtedly,  with  increas- 
ing dilution  and  increasing  temperature,  an  increasing  fraction  of 
free  alkali  formed.  This  is  the  consequence  of  the  better  condi- 
tions offered  for  hydrolysis  of  the  soap  into  free  alkali  and  free 
fatty  acid.  But  the  mass  which  separates  on  cooling  is  certainly  no 
true  bipalmitate,  for  chemical  reasons  alone  make  it  hard  to  see 
how  a  monovalent  fatty  acid  can  give  rise  to  "  acid  "  salts.  The 
separated  mass  is  not  a  chemical  compound,  but  simply  free  fatty 
acid  with  which  has  been  admixed  mechanically  a  smaller  and 
smaller  amount  of  neutral  soap. 

What  has  been  said  of  sodium  palmitate  holds  also  for  sodium 
stearate  and  for  all  the  higher  members  of  the  acetic  series.  It  is 
true  also  for  sodium  oleate.  The  amount  of  such  hydrolysis, 
however,  decreases  as  the  acetic  series  is  descended  so  that  for 
sodium  caprate  and  for  .soaps  lying  below  this  it  is  very  small 
indeed.  Were  we  to  convert  this  finding  into  the  terms  of  "  pro- 
tein "  "  coagulation,"  we  would  have  to  say  that  the  "  protein  " 
1  KRAFFT:  Ber.  d.  deut.  chem.  Gesellsch.,  27,  1747  (1894). 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  233 

is  no  longer  heat-coagulable.  The  analog  for  the  behavior  of 
soaps  of  this  type  may  be  found  in  the  basic  derivatives  of  certain 
globulins. 

§4 

We  wish,  finally,  to  touch  upon  some  biological  coagulations 
in  an  attempt  to  define  their  nature  more  closely  in  the  terms  of 
colloid-chemistry.  Reference  is  made  to  the  coagulations  typical 
of  blood,  milk  and  muscle  juice.  In  all  these  instances  a  protein 
body  (fibrinogen,  caseinogen,  myosinogen)  passes  from  a  "  sol- 
uble "  state  to  an  "  insoluble  "  clot  (fibrin,  casein,  myosin).  Be- 
tween the  two  extremes,  however,  the  originally  liquid  "  plasma  " 
sets  into  a  jelly  which  gradually  develops  signs  of  contracting  with 
the  squeezing  off  of  a  "  serum."  The  clot  finally  swims  in  this 
serum  as  a  relatively  anhydrous  mass.  It  is  not  our  purpose  to 
enter  into  the  debate  concerning  the  chemical  nature  of  the 
various  elements  which  are  necessary  for  such  coagulation.  All 
authors  seem  to  agree  that  a  substance  x  ("  fibrin  ferment,"  ren- 
nin,  muscle  ferment)  acts  upon  a  second  (fibrinogen,  caseinogen, 
myosinogen)  to  produce  the  clot,  the  production  of  the  latter 
being  greatly  favored  by  the  presence  of  some  of  the  earthy  or 
heavier  metals  such  as  calcium  or  iron.  It  would  not  yet  "  explain  " 
the  physical  changes  accompanying  the  transformation  of  fibrino- 
gen into  fibrin  even  if  it  were  proved  (or  disproved)  that  fibrin  is 
a  true  chemical  union  between  calcium  and  fibrinogen. 

It  will  be  apparent  that  the  entire  set  of  physical  changes  are  such 
as  may  be  observed  in  the  simple  salting-out  of  a  soap  l  and  whatever 
the  ultimately  accepted  chemical  fundaments  of  "  clotting,"  the 
physical  transformation  in  the  system  must  be  of  the  same  general 
type  as  observed  in  the  salting-out  of  a  soap.  It  is  necessary,  in  con- 
sequence, to  look  at  the  soap  system  once  more  (see  Fig.  74),  to 
grasp  correctly  the  analogous  changes  in  protein  systems  when 
these  "  clot." 

The  liquid  "  plasma  "  of  blood,  milk  or  muscle  juice  is  analogous 
to  a  liquid  colloid  system  of  the  type  sodium  oleate/water.  The 
substance  x  (fibrin  ferment,  rennin,  muscle  ferment)  which  will 
bring  about  clotting  may  be  anything  which  will  lead  to  the  sep- 
aration of  a  second  phase  within  the  hydrated  sodium  oleate. 
It  must  hi  consequence  be  either  (1)  a  substance  which,  like  sodium 

1  See  page  113. 


234  SOAPS  AND  PROTEINS 

chlorid,  combines  with  water  while  depriving  the  sodium  oleate 
of  its  water  or  (2)  one  which  acts  upon  the  sodium  oleate  (like  a 
weak  acid)  to  produce  from  it  a  new  substance  (like  fatty  acid) 
which  remains  emulsified  in  the  unchanged  hydrated  sodium 
oleate.  In  either  instance  the  viscosity  of  the  whole  system 
must  rise,  as  exemplified  in  the  first  stages  of  the  salting-out  of  a 
soap  or  in  the  increase  in  viscosity  observed  whenever  a  "  mayon- 
naise "  is  made  by  emulsification  of  a  fat  or  fat-like  body  (fatty 
acid)  in  a  hydrated  soap  or  hydrated  protein.  With  addition  of 
more  salt  or  more  fat-like  body  the  type  of  emulsion  changes  to 
one  of  soap-in-oil  and  as  this  occurs  the  viscosity  of  the  system 
falls,  "  serum  "  separates  off  and  the  soap  or  fatty  acid  swims  as 
a  clot  to  the  top.  If  the  soap  or  fatty  acid  is  crystalline  at  the 
temperature  of  the  clotting  it  may,  of  course,  crystallize  out.  It 
is  of  interest  therefore  to  note  that  in  the  case  of  blood  coagulation 
the  clot  is  definitely  crystalline.1 

We  do  not  presume  to  say  which  of  the  two  types  of  "  coagu- 
lant," the  "  fibrin  ferment,"  rennin  or  muscle  ferment  follows,  but 
we  incline  to  the  view  that  it  probably  acts  like  a  weak  acid  which 
splits  the  original  fibrinogen  (and  not  like  the  salt).  The  "  fer- 
ment "  nature  of  the  different  coagulants  has  been  seriously  ques- 
tioned in  late  years,  for  they  not  only  seem  heat  stabile,  but 
disappear  quantitatively  as  coagulation  advances.  It  is  not 
necessary,  of  course,  that  such  "  splitting  "  should  be  induced 
through  a  true  ferment.  The  appearance  in  the  reaction  mixture 
of  any  substance  which  acts  like  a  weak  acid  would  do  quite  as 
well,  for  the  addition  of  a  limited  amount  of  such  a  substance  will 
not  only  stiffen  a  hydrated  soap/water  system  but,  similarly,  any 
hydrated  potassium,  sodium  or  other  basic  proteinate  system,  as 
illustrated,  for  example,  in  the  "  souring  "  of  milk. 

How  now  may  the  "  favoring  "  action  upon  coagulation  of 
calcium,  iron  or  other  heavier  salts  be  understood?  It  is  necessary, 
here,  to  state  just  which  part  of  the  coagulatory  process  is  "  fav- 
ored." Usually  it  means  the  earlier  appearance  of  a  free  clot  or 
the  development  of  a  "  firmer  "  clot.  Obviously  the  presence  of 
the  heavier  metals  must  favor  the  development  of  fatty  acid  or 
proteinic  acid  derivatives  which  are  possessed  of  low  hydration 
capacities. 

'See  SrtteEL:  Pfluger's  Arch.,  156,  361  (1914);  W.  H.  HOWELL:  Am. 
Jour.  Physiol.,  36,  143  (1914). 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  235 


II 

ON   THE   THEORY   OF   POISONING   BY  AMMONIUM 
COMPOUNDS   AND   BY  HEAVY   METALS 

1.  General  Remarks 

If  we  may  apply  to  protoplasm  the  conclusions  which  have 
been  reached  in  the  previous  pages  it  seems  safe  to  us  to  say  that 
the  foundation  of  living  matter  is  a  polymerized  amino- (fatty )- 
acid  to  which  normally  are  joined  various  bases  (like  potassium, 
sodium,  magnesium  and  calcium)  and  various  acid  radicals  (like 
chlorid,  bromid,  bicarbonate,  sulphate  and  phosphate)  the  whole 
constituting  a  unit l  capable  of  sucking  up  or  "  dissolving  "  a 
certain  amount  of  water.  It  is  in  other  words  a  basic-protein- 
acid  compound  in  which  water  has  been  dissolved.  Even  the 
blood  and  the  lymph  have  this  colloid-chemical  constitution. 
The  secretions  from  the  body,  on  the  other  hand,  represent  the 
opposite  type  of  system — the  urine  and  sweat,  for  example,  are 
essentially  "  solutions  "  of  protoplasmic  material  in  water. 

It  is  of  interest  now  to  study  this  hydrated  protoplasmic  mass 
(tissue  and  blood)  to  see  what  changes  it  may  suffer  when  other 
than  the  normal  bases  or  acids  are  introduced  into  it  or  the  pro- 
portions of  these  constituents  to  each  other  are  varied  from  the 
normal.  Proper  answer  here  has  much  to  do  with  our  funda- 
mental theories  of  the  physiology  and  pathology  of  cell  behavior 
and  of  pharmacological  action. 

1  From  constant  repetition  in  colloid-chemical,  physiological  and  pharma- 
cological action  the  grouping  may  be  expressed  approximately  as  follows: 

/NH4 
x — COOH<  K 

\Na 

NH2  Mg 

/\  Ca 

HSCN  Ba  (?) 

HC1  Fe 

HBr  Pb 

HI  (?)  Hg 

HC2H3O2 
H2S04 
H3P04 


236  SOAPS  AND  PROTEINS 

It  is  worthy  of  note,  first,  that  sodium  and  chlorid  are  among 
the  least  poisonous  of  the  listed  constituents  that  may  be  intro- 
duced into  cell  protoplasm.  It  is  for  this  reason  that  sodium 
chlorid  is  the  main  component  of  all  "  physiological  "  salt  solu- 
tions.1 Not  only  do  sodium  and  chlorid  appear  in  protoplasm 
in  largest  amounts  (in  the  list  of  the  so-called  inorganic  "  salts  ") 
but  they  yield,  with  protein,  colloid  systems  which  in  physical 
behavior  most  closely  approximate  the  physical  characteristics 
of  living  matter.  As  we  ascend  or  descend  the  list  of  the  tabulated 
bases  or  acids  from  sodium  or  chlorid  we  encounter  protein  deriv- 
atives which  are  either  more  hydratable  and  soluble  in  water  than 
normal  protoplasm  or  which  are  less  hydratable  and  soluble.  It  is 
this  fad,  we  think,  which  is  associated  with  the  physiological,  patho- 
logical and  pharmacological  action  of  these  elements  when  introduced 
in  more  than  normal  concentration  into  the  living  mass.  When, 
for  example,  potassium  is  introduced  in  more  than  normal  amount 
it  exerts  a  "  poisonous  "  action  which  colloid-chemically  evi- 
dences itself  through  an  increased  swelling  and  an  increased 
fluidity  of  the  affected  protoplasm.  Ammonium  acts  similarly, 
which  explains  why  potassium  and  ammonium  salts,  for  example, 
are  used  therapeutically  to  render  more  liquid  the  mucinous 
secretions  of  "  catarrhally  "  affected  mucous  membranes. 

1  In  connection  with  the  analysis  of  physiological  and  pathological  prob- 
lems in  the  terms  of  colloid-chemistry,  definition  must  be  attempted  of  the 
nature  of  such  "physiological"  salt  solutions.  Pure  water  is  poisonous 
because  in  contact  with  it,  protoplasm  hydrolyzes.  Free  protein  in  conse- 
quence precipitates  within  the  cell  while  "salts"  diffuse  into  the  distilled 
water.  Presence  of  any  salt  in  the  pure  water  reduces  such  hydrolysis.  The 
salt  must,  however,  be  of  such  nature  and  of  such  concentration  as  not  to 
diffuse  into  the  protoplasm  and  displace  the  normal  equilibrium  existing 
there  between  the  various  basic  and  acidic  elements.  Hence  the  superior 
value  of  an  NaCl  solution  over  that  of  any  other  one  salt.  But  NaCl  alone 
still  permits  of  displacements  and  loss  to  the  salt  solution  of  constituents  like 
K,  Ca,  HjCOa,  etc.  For  this  reason  a  RINGER  solution  (which  contains  small 
amounts  of  each  of  these  in  addition  to  NaCl)  is  superior  to  simple  salt  solu- 
tion. Solutions  of  the  sugars  (even  when  present  in  the  same  "osmotic" 
concentration)  do  not  prevent  such  hydrolysis  and  hence  are  little  better 
than  distilled  water.  When  properly  prepared,  a  physiological  salt  solution 
will  have  a  composition  which,  as  a  solution  of  salts  in  water,  is  in  equilibrium 
with  the  system,  solution  of  water  in  protoplasm.  The  protoplasm  will 
now  neither  take  up  nor  give  off  water,  in  other  words  the  two  systems 
will  be  "  iso tonic."  The  concentration  of  the  individual  salts  in  the  water 
will,  however,  probably  not  be  (and  need  not  be)  that  of  the  concentration  of 
these  same  elements  in  the  hydrated  protoplasmic  mass.  Whence  the  com- 
mon finding  that  "isotonic"  solutions  are  rarely  (if  ever!)  isosmotic. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  237 

The  introduction  of  magnesium  or  calcium  into  protoplasm 
leads,  on  the  other  hand,  to  a  "  drying  out  "  of  the  protoplasmic 
mass.  While  small  amounts  of  these  elements  are  necessary 
to  maintain  protoplasm  in  its  normal  state,  larger  ones  begin 
to  show  a  distinctly  "  poisonous  "  action.  Such  poisonous  effect, 
with  corresponding  dehydration  of  the  tissues,  jumps  enormously 
when  salts  of  iron,  silver,  mercury  or  lead  are  used  in  pharma- 
cological practice;  hence  the  need  of  administering  these  sub- 
stances in  very  small  amounts,  in  medicine,  if  their  use  is  not 
to  be  pushed  beyond  the  "  physiological  limit." 

In  the  case  of  the  heavier  metals,  the  above  considerations 
lead  us  to  the  obvious  conclusion  that  these  act  as  poisons  to 
protoplasm  because  they  unite  with  protoplasm  to  form  compounds 
more  sparsely  hydratable  than  normal  protoplasm.  In  pathol- 
ogy and  medical  practice  the  formation  of  such  heavy  metal 
protoplasmic  compounds  is  generally  considered  to  constitute 
an  irreversible  change  and  the  affected  protoplasm  is  commonly 
adjudged  necrotic  or  dead.  The  mere  fact,  however,  that  indi- 
viduals poisoned  by  any  of  the  heavy  metals  do  occasionally 
recover  already  indicates  that  such  a  conclusion  overstates  the 
facts;  it  was  learned,  moreover,  in  considering  the  colloid-chemical 
behavior  of  the  analogous  heavy  metal  soaps,  that  these  could 
be  converted  into  light  metal  soaps.  We  wish  now  to  show  that 
the  heavy  metal  proteinates  with  their  low  hydration  capacities  can 
also  be  converted  into  the  more  highly  hydratable  lighter  metal  pro- 
teinates and  that,  as  the  latter  are  formed,  colloid-chemical  restitu- 
tion to  the  condition  which  more  nearly  approximates  the  physio- 
logical state  of  protoplasm  may  be  obtained.  Before  pointing 
out  the  obvious  theory  of  intoxication  and  detoxication  to  which 
this  fact  leads,  some  experiments  of  ROBERT  A.  KEHOE  *  must 
be  detailed. 

2.  Experiments  on  the  Conversion  of  Heavy  Metal  Proteinates 
into  Light  Metal  Proteinates 

A  measured  amount  (5  cc.)  of  a  viscid  gelatin  (2  grams  in 

100  cc.  water)  was  gently  stirred  together  with  an  equal  volume 

of  distilled  water  or  an  equal  volume  of  m/500  silver  nitrate. 

The  appearance  of  five  tubes  forty-eight  hours  after  being  thus 

1  ROBERT  A.  KEHOE:   Jour.  Lab.  and  Clin.  Med.,  5,  443  (1920). 


238  SOAPS  AND  PROTEINS 

prepared  is  shown  in  the  upper  row  of  Fig.  111.  The  tube  on  the 
left  contains  the  gelatin-water  control,  the  remaining  tubes 
gelatin  and  silver  nitrate.  There  was  now  added  to  the  tubes, 
respectively  from  left  to  right,  5  cc.  water,  5  cc.  water,  5  cc.  m/3 
sodium  sulphate,  5  cc.  m/3  magnesium  sulphate,  5  cc.  m/10 
potassium  hydroxid.  The  lower  row  of  Fig.  Ill  shows  the  effects 
of  such  treatment  thirty-six  hours  later.  The  first  two  tubes 
are  obviously  unchanged.  There  has  been  distinct  recession  of 
the  coagulating  effects  of  the  silver  in  the  remaining  tubes,  restitu- 
tion in  the  case  of  the  KOH  being  apparently  complete. 


FIGURE  111. 

Fig.  112  shows  the  reversing  effects  of  these  and  other  lighter 
metal  salts  when  added  to  a  series  of  2  percent  gelatin  solutions 
(5  cc.  each)  previously  coagulated  through  the  addition  of  an 
equal  volume  of  m/500  cupric  sulphate,  m/1500  ferric  sulphate, 
m/1000  plumbic  chlorid.  After  the  coagulants  had  acted  for 
forty-eight  hours  the  reversing  agents  (5  cc.  each)  were  added 
to  the  tubes  (m  Nal,  2  m  MgCl2,  m/20  KOH,  2  m  KC1,  2  m 
MgCl2,  m/20  KOH,  2  m  KBr,  2  m  KC1,  m/20  KOH).  The 
photograph  portrays  the  tubes  twenty-four  hours  after  such  addi- 
tion. The  clear  gelatin  control  appears  on  the  extreme  left. 
The  unchanged  heavy  metal  controls  are  the  left-hand  tubes  in 
each  of  the  remaining  groups.  The  three  remaining  tubes  of 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES 


239 


each  of  the  series  show  that  complete  resolution  of  the  original 
heavy    metal    coagulum    has 
been  obtained  in  all  cases. 

The  importance  of  using 
enough  of  the  lighter  metal 
salts  if  reversion  is  to  be  ac- 
complished is  illustrated  for 
mercury  coagulation  in  Fig. 
113.  With  the  exception  of 
the  pure  gelatin  control,  all 
the  tubes  contained  5  cc.  of  2 
percent  gelatin  to  which  had 
been  added  5  cc.  m/1000  mer- 
curic chlorid.  Twenty-four 
hours  later  5  cc.  distilled  water 
were  added  to  the  pure  gelatin 
and  a  mercury  gelatin  control; 
to  the  remaining  tubes  were 
added  5  cc.  of  potassium  iodid 
of  the  concentrations  m/1, 
m/2,  m/4,  m/8  and  m/32. 
The  photograph  taken  twenty- 
four  hours  later  shows  complete 
reversal  of  the  coagulation  only 
for  the  tube  to  which  m/1 
potassium  iodid  was  added  and 
less  and  less  reversion  as  the 
concentration  of  the  reversing 
salt  was  lowered. 

Lest  it  be  thought  that 
these  observations  on  "  dead  " 
proteins  do  not  apply  to  "  liv- 
ing "  tissues  the  following  ob- 
servations of  KEHOE  1  may  be 
of  interest.  The  enzymatic 
reactions  are  perhaps  as  charac- 
teristic of  li ving  matter  as  any. 
KEHOE  finds  that  the  starch- 
splitting  activity  of  saliva  may 

1  ROBERT  A.  KEHOE:  Personal  communication  (1921). 


IN 


240 


SOAPS  AND  PROTEINS 


be  "  killed  "  through  the  addition  of  various  heavy  metals.  Saliva, 
thus  "  poisoned  "  for  weeks,  will  again  split  starches  to  dextrose 
when  any  of  the  light  metal  salts  are  added  to  it.  But  here  again 
interesting  differences  appear.  While  all  the  lighter  metals  act 
in  this  fashion,  excessive  addition  of  such  metals  as  potassium 
will  again  kill  the  reaction.  Apparently  only  when  the  enzyme 
'presumably  a  protein)  has  a  medium  grade  of  dispersion  and 


FIGURE  113. 

hydration  and  not  an  excessive  one  with  excessive  solubility  in 
water  will  it  best  exhibit  its  starch-splitting  properties.1 

3.  On  the  Nature  and  Relief  of  Heavy  Metal  Poisoning 

§1 

It  is  perhaps  fair  to  say  that  the  present  day  treatment  of  heavy 
metal  poisoning  is  an  attempt,  in  the  main,  to  discover  some 

1  This  idea  that  optimal  enzymatic  activity  is  associated  with  a  certain 
degree  of  dispersion  of  the  enzyme,  independently  arrived  at  by  KEHOE, 
was  first  discovered  through  other  colloid-chemical  methods  by  A.  FODOR 
(Fermentforschung,  4,  191,  209  (1920)).  FODOR  found  that  the  enzymatic 
activity  (digestion  of  polypeptids)  and  ultramicroscopic  picture  of  a  phos- 
phoprotein  obtained  from  yeast  was  destroyed  through  the  action  of  much 
acid  but  that  both  could  be  restored  through  neutralization  of  the  acid  and 
addition  of  KC1. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  241 

"  antidote  "  which  will  throw  the  poisonous  agent  "  out  of  solu- 
tion "  in  "  insoluble  "  form.  Many  facts  in  chemistry,  pharma- 
cology and  therapy  already  suffice  to  indicate  that  such  a  notion 
regarding  the  action  of  antidotal  agents  is  incorrect.  Unless,  for 
example,  an  exactly  proper  concentration  is  maintained,  the  admin- 
istration of  sodium  or  potassium  iodid  to  individuals  poisoned 
with  lead  or  mercury  does  not  result  in  the  formation  of  insoluble 
lead  or  mercury  salts,  but  may  quite  as  easily  yield  soluble  products. 
And  yet  the  beneficent  effects  of  iodid  administration  in  the  relief 
of  various  heavy  metal  intoxications,  even  when  such  concen- 
tration details  are  ignored,  cannot  be  doubted.  In  the  experi- 
ments of  KEHOE  the  concentration  of  the  reversing  salts  was  so 
chosen  as  to  yield  no  precipitates  of  the  heavy  metal  elements, 
and  yet  the  more  normal  state  of  the  previously  coagulated  pro- 
tein was  undoubtedly  restored. 

The  heavy  metal  salts  do  not  poison  protoplasm  because  they  are 
dissolved  in  it,  but  because  they  combine  with  the  protein  constituents 
of  the  cell  to  yield  insoluble  proteinates  of  low  hydration  capacity. 
Antidotes  do  not  save  such  poisoned  cells  because  they  precipitate  the 
heavy  metal,  but  because  they  displace  the  heavy  metal  from  its  protein 
combination  to  unite  themselves  with  the  protein  freed.  The  heavy 
metal  previously  insoluble  because  united  to  the  protoplasm  of 
the  cell  again  becomes  soluble  and  as  such  may  be  washed  out  of 
the  body. 

§2 

The  above  considerations  bring  with  them,  we  think,  sug- 
gestions of  practical  value  for  the  treatment  of  all  the  heavy  metal 
poisonings. 

It  is  obvious  that  if  the  heavy  metal  proteinates  revert  under 
the  influence  of  light  metal  salts  to  the  proteinates  of  these  lighter 
metals  (which  then  more  nearly  approximate  in  physical  state  the 
proteins  of  the  normal  cell)  a  second  reason  appears  for  the  admin- 
istration of  large  doses  of  alkali  to  patients  poisoned  by  the  heavy 
metals.  A  first  reason  was  found  and  utilized  some  years  ago  1 
when  the  administration  of  alkali  was  recommended  to  patients 

1  MARTIN  H.  FISCHER:  (Edema,  123,  133,  New  York  (1910);  Nephritis, 
52,  125,  173,  186,  New  York  (1912);  (Edema  and  Nephritis,  2nd  Ed.,  549, 
648,  New  York  (1915);  (Edema  and  Nephritis,  3rd  Ed.,  727,  789,  New  York 
(1921).  Here  numerous  references  to  the  older  literature  may  be  found. 


242  SOAPS  AND  PROTEINS 

poisoned  (or  about  to  be  poisoned  for  therapeutic  reasons)  by 
arsenic,  mercury  or  lead.  As  discovered  by  F.  HOPPE-SEYLER 
and  his  pupils,  T.  ABAKI,  T.  IRASAWA  and  H.  ZILLESSEN,  the  heavy 
metals  interfere  with  the  normal  oxidation  chemistry  of  living 
cells,  resulting  in  an  abnormal  production  and  accumulation  of 
acids  in  the  involved  cells.  Such  increased  acid  content  is  fol- 
lowed by  an  increased  water  absorption  (cedema)  of  the  involved 
cells  which  in  the  case  of  such  organs  as  the  brain,  medulla  and 
kidney  may  lead  to  a  fatal  issue.  Associated  with  this  phar- 
macological action  of  the  heavy  metals  and  the  swelling  of  certain 
proteins  is  their  other  colloid-chemical  action  which  results  in  the 
formation  of  less  hydratabk  compounds  (like  the  metallic  globu- 
linates).  The  combination  of  the  swelling  of  certain  proteins 
with  the  dehydration  of  others  yields  the  anatomical  picture  which 
the  pathologists  call  "  cloudy  swelling."  To  neutralize  the 
acids  formed  and  thus  to  reduce  the  swelling  of  the  one  while  at 
the  same  time  the  attempt  is  made  to  uncoagulate  the  dehydrated 
second  and  thus  clear  the  "  clouding,"  heavy  doses  of  alkali  are 
needed  (like  the  bicarbonates,  carbonates  and  hydroxids  of  sodium, 
potassium  and  magnesium  or,  in  general,  any  of  the  lighter  bases  in 
combination  with  organic  acids  oxidizable  to  carbonates).  These 
substances  alone,  or  better  in  mixture,  must  be  given  in  sufficient 
amounts  day  and  night  to  maintain  a  permanently  neutral  or  even 
a  slightly  alkaline  reaction  of  the  urine.  In  order  to  float  off  in 
solution  the  liberated  heavy  metal,  water  is  needed.  It  must, 
however,  be  remembered  that  water  alone,  especially  when  brought 
in  contact  with  cells  inclined  to  cedema,  favors  their  swelling  and 
solution.  To  offset  such  deleterious  effects,  the  alkaline  salts  and 
water  intake  must  be  so  controlled  (whether  given  by  mouth, 
rectum  or  intravenously)  as  always  to  have  the  combination  touch 
the  affected  cells  in  hypertonic  solution.  J  How  much  may  be 
accomplished  in  saving  an  extra  fraction  of  those  poisoned  by  the 
heavy  metals  by  such  methods  may  be  deduced  not  only  from  my 
own  studies 2  but  from  the  independent  ones  of  WILLIAM  DEB. 
MACNIDER  and  H.  B.  WEiss.3 

1  For  details  regarding  such  treatment  see  MARTIN  H.  FISCHER:    (Edema 
and  Nephritis,  3rd  Ed.,  667,  678,  783,  New  York  (1921). 

2  MARTIN  H.  FISCHER:    (Edema,  123,  133,  New  York  (1910);   Nephritis, 
52,  125,  173,  186,  New  York  (1912);    (Edema  and   Nephritis,  2nd  Ed.,  549, 
648,  New  York  (1915);    (Edema  and  Nephritis,  3rd  Ed.,  727,  789,  New  York 
(1921). 

•WILLIAM   DEB.  MACNIDER:  Jour.  Exp.  Med.,  23,  171  (1916);  ibid.,  26, 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  243 

4.  Concluding  Remarks 

In  these  concluding  paragraphs  we  shall  in  rather  dogmatic 
fashion  try  to  group  the  results  of  the  studies  outlined  in  these 
pages  with  some  older  ones,1  all  of  which  had  in  common  the  pur- 
pose of  analyzing  protoplasm  colloid-chemically  and  of  denning 
as  accurately  as  possible  the  nature  of  various  changes  observable 
in  the  living  mass  when  subjected  to  physiological  or  pathological 
change. 

§1 

Biological  evidence  indicates  that  of  the  five  proximate  prin- 
ciples found  in  protoplasm, — protein,  carbohydrate,  fat,  salt  and 
water — three  constitute  an  irreducible  minimum.  While  life 
may  continue  in  the  absence  of  carbohydrate  and  fat  it  ceases 
as  soon  as  any  of  the  other  three  is  missing.  What  is  the  relation- 
ship of  these  to  each  other?  In  the  common  belief  these  materials 
exist  "  in  dilute  solution  "  in  the  cells  which,  plainly  put,  are  held 
to  be  little  bags  of  salt  solution  in  which  the  proteins  are  either 
dissolved  or  "  suspended."  And  yet,  normal  protoplasm  even 
when  very  rich  in  salts  has  not  a  salty  taste  and  does  not  yield 
any  appreciable  portion  of  its  salt  content  to  rain  or  dew 2  or 
the  distilled  water  in  which  it  may  be  bathed.  The  salts  are 
obviously  not  in  dilute  solution  but  combined  with  the  protein. 
Biological  reasoning  therefore  compels  the  same  conclusion 
to  which  the  analogies  existent  between  the  behavior  of  simple 
(protein)  colloid  systems  and  the  behavior  of  living  matter  have 
led  us.  The  so-called  "  salts  "  and  the  water  of  protoplasm  (except 
in  theoretical  amounts)  are  not  "free."  The  salts  are  combined  with 
the  proteins  and  the  combination  is  not  "  dissolved  "  in  water,  but 
conversely,  water  is  dissolved  in  it.  Living  matter  is  in  essence  a 
unit,  a  hydrated  basic-protein-acid  complex  in  which  ionization, 
the  laws  of  true  solution  and  the  presence  of  water  in  a  state 
analogous  to  that  seen  in  a  glass  are  reduced  practically  to  zero.3 

1,  19  (1917);  ibid.,  28,  50,  517  (1918);  Proc.  Soc.  Exp.  Biol.  and  Med.,  14, 
140  (1917);  H.  B.  WEISS:  Jour.  Am.  Med.  Assn.,  68,  1618  (1917);  ibid.,  71, 
1045  (1918). 

1  MARTIN  H.  FISCHER  and  MARIAN  O.  HOOKER:   Fats  and  Fatty  Degen- 
eration, New  York  (1917);    MARTIN  H.  FISCHER:    (Edema   and  Nephritis, 
3rd  Ed.,  New  York  (1921). 

2  See  JOHN  URI  LLOYD:  Eclectic  Med.  Jour.,  75,  616  (1915). 

3  What  is  said  here  of  the  "salts" — which  obviously  are  made  when  pro- 


244  SOAPS  AND  PROTEINS 

It  is  as  different  from  the  ordinary  dilute  solution  as  a  "  solution  " 
of  water  in  phenol  is  different  from  one  of  phenol  in  water. 

The  experiments  detailed  in  the  preceding  pages  also  indicate 
how  the  colloid-chemical  nature  of  this  hydrated  protein  colloid 
which  constitutes  the  physiological  basis  of  life  may  be  changed, 
either  from  within  or  without,  so  as  to  give  rise  to  the  manifesta- 
tions of  physiology,  or,  when  more  accentuated,  of  pathology. 
Through  temporarily  or  more  continuously  acting  factors,  be  they 
mild  or  drastic  in  their  action,  the  chemical  character  of  protoplasm 
is  changed  and  depending  upon  the  hydration  and  solution  character- 
istics of  the  new  compounds  formed,  the  physical  state  of  the  living 
mass  is  also  changed. 

In  the  list  of  the  simpler  changes  which  may  thus  be  brought 
about  are  those  which  give  character  to  oedema  and  abnormal 
water  loss.  The  protoplasmic  mass  which  in  its  "  normal  "  state 
has  sucked  up  as  much  water  as  it  can,  is  possessed  of  what  the 
physiologists  call  a  normal  water  content  or  a  normal  turgor. 
If,  for  any  reason,  a  cell  takes  up  more  than  this  normal  amount 
of  water,  it  becomes  "  cedematous."  The  botanists  say  that 
the  cell  is  then  in  a  state  of  abnormally  high  turgor  which,  when 
extreme,  results  in  destruction  of  the  cell  or  "  plasmoptysis." 
Obviously,  anything  which  under  physiological  or  pathological 
conditions  brings  about  such  change  in  the  colloid  mass,  which, 
in  other  words,  enables  it  to  absorb  such  excessive  amounts  of 
water  may  be  listed  as  a  "  cause  "  of  cedema  or  increased  turgor. 

For  this  reason  abnormal  accumulations  of  acids  or  of  alkalies 
within  a  cell  may  be  listed  as  causes  for  cedema,  for  these  so  act 
upon  the  "  normal  "  albumins  of  the  cell  as  to  convert  them 
into  albuminates  which  have  a  higher  hydration  capacity.  But 
the  amins,  pyridin  and  urea  also  increase  the  hydration  capacity 
of  proteins  (though  in  a  different  way)  so  they,  too,  are  in  pro- 
portion to  their  activity,  "  causes  "  for  cedema.  Or  when  one 
basic  or  acid  radical  is  substituted  for  another  in  the  normal 
protoplasm  this  may  be  a  cause  for  cedema;  for  ammonium  or 
potassium  proteinates  are  more  hydratable  than  sodium  or  mag- 
nesium proteinates,  and  protein  chlorid  swells  more  than  protein 

toplasm  is  subjected  to  drying  out,  to  the  action  of  water,  or  to  the  action  of 
analytical  agents,  is  to  our  minds  true  also  of  many  other  components  held  to 
be  preexistent  and  "dissolved"  in  living  matter.  Alkaloids  certainly  do 
not  exist  as  such  in  normal  protoplasm — they  are  split  off  through  the  methods 
used  to  isolate  them  as  JOHN  URI  LLOYD  has  so  often  insisted. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  245 

sulphate.  Such  facts  explain  the  "  poisonous  "  and  swelling  effects 
of  pure  potassium  or  pure  chlorid  solutions  upon  normal  cells 
which  on  exposure  to  these  lose  their  sodium  and  calcium  or  their 
sulphate  and  phosphate,  etc. 

On  the  other  hand,  anything  which  decreases  the  water  hold- 
ing power  of  the  protoplasmic  colloids  is  to  be  listed  as  a  cause 
for  "  abnormal  water  loss,"  for  shrinkage  of  the  cell  or,  to  use 
the  terminology  of  the  botanists,  "  plasmolysis"  Much  effort 
has  been  made  to  bring  these  swellings  and  shrinkings  into  rela- 
tionship with  the  laws  of  osmotic  pressure.  That  all  such  attempts 
have  failed  will  surprise  no  one, — the  laws  governing  the  water- 
holding  powers  of  cells  are  the  laws  which  govern  the  water- 
holding  powers  of  their  "  normal  "  colloid  proteins  and  protein- 
ates  and  of  the  new  colloid  derivatives  produced  from  these  when 
exposed  to  the  action  of  different  salts.  Since  the  derivatives 
produced  are  possessed  of  entirely  different  hydration  capacities 
even  when  the  salts  are  applied  in  the  same  concentration  the 
ultimate  swellings  and  shrinkings  must  obviously  also  be  dif- 
ferent in  spite  of  equivalence  in  "  osmotic  pressure." 

As  we  previously  listed  various  elements  as  "  causes "  of 
cedema  we  could  now  in  similar  fashion  list  others  as  causes  of 
plasmolysis.  In  sufficient  concentration  all  salts  are  such,  but 
in  their  mode  of  action  we  must  distinguish  between  at  least 
two  types  of  effects.  Even  without  entering  the  protoplasmic 
mass,  salt  molecules  may  bind  water  and  so  take  it  away  from 
the  hydrated  protoplasmic  mass  (shrinking  it  through  "depriv- 
ation of  solvent"  as  first  suggested  by  FRANZ  HOFMEISTER  *); 
on  the  other  hand  the  salt  radicals  may  replace  others  in  the 
protoplasmic  mass  binding  themselves  to  the  vacated  bonds. 
In  this  way  lead,  mercury  and  similar  proteinates  are  produced 
which,  as  compared  with  the  more  "  normal  "  potassium,  sodium 
and  magnesium  proteinates,  suck  up  scarcely  any  water  at  all. 

§2 

The     colloid-chemical     variations     accompanying     chemical 
change    in  the  fundament  of  the    living  cell  are  not,  however, 
exhausted  by  this  change  in  its  water-holding  power.     Its  solu- 
bility in  water  also  changes.     Generally  speaking  those  proto- 
1  FRANZ  HOFMEISTER:  Arch.  f.  exp.  Path.  u.  Pharm.,  25,  6  (1888). 


246  SOAPS  AND  PROTEINS 

plasmic  derivatives  which  have  a  greater  capacity  for  swelling 
have  also  a  greater  tendency  to  "  go  into  solution."  The  things 
that  make  for  cedema  make  also,  therefore,  for  the  appearance  of 
protein  ("  albumin  ")  in  the  surrounding  medium.  The  swollen 
kidney  in  nephritis  therefore  yields  albumin  to  the  urine  (albumin- 
uria);  the  oedematous  brain  or  spinal  cord  makes  the  protein 
content  of  the  spinal  fluid  go  up;  etc. 

§3 

In  association  with  these  changes  in  the  direction  of  increased 
swelling  and  increased  solubility,  or  decreased  swelling  and 
decreased  solubility,  it  is  well  to  carry  in  mind  a  third  type  of 
change  to  be  considered  whenever  salt  in  rather  high  concentra- 
tion is  added  to  protoplasm  and  when  the  possibilities  for  chemical 
reaction  between  the  salt  and  the  protoplasm  are  practically 
^^^_^^  zero.  The  change  about  to  be  de- 
scribed scarcely  appears  when  the 
normal  (relatively  dry)  cell  is  up  for 
consideration;  it  may  be  prominent 

0°°l     )  o~       when  the  cell  is  oedematous  (or  prac- 
o^o^-^o  o       tically    liquid).       When    a    chemically 
non-active  salt  is  applied  to  protoplasm 
B  in  relatively  high  concentration  it  tends 

FIGURE  114.  to    shrink    the    normal    cell    (see  A  of 

Fig.   114)    concentrically;    when  mixed 

with  a  more  liquid  protoplasm  the  salt  particles  unite  with  water 
within  the  protoplasmic  mass  (see  B  of  Fig.  114).  Dehydration 
of  the  (protein)  colloids  of  the  cell  occurs  in  both  instances,  but 
volume  change  (in  the  sense  of  a  decrease)  may  not  appear  in  the 
second. 

The  matter  is  of  much  importance  in  the  analysis  of  the  princi- 
ples which  must  guide  us  in  the  treatment  of  cedema.  As  so 
often  insisted,  all  salts,  including  sodium  chlorid,  decrease  the 
hydration  capacity  of  a  protein  in  the  presence  of  an  acid  and 
for  this  reason  should  be  administered  in  as  high  a  concentration 
as  possible  to  the  oedematous  individual.  It  has,  however,  been 
insisted  by  various  clinicians  that  the  administration  of  salts 
(especially  sodium  chlorid)  does  not  decrease,  but  may  actually 
increase  oedema.  While  many  of  the  observations  intended  to 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  247 

prove  this  point  are  subject  to  serious  question,  the  observations 
detailed  in  this  volume  1  show  how  such  occasional  findings  may 
be  explained. 

After  the  state  described  in  B  of  Fig.  114  has  been  attained 
it  needs  to  be  remembered  that  every  salt  water  droplet  is  enclosed 
within  a  hydrated  colloid  membrane.  But  these  are  now  osmotic 
systems;  for  the  so-called  semipermeable  membranes  of  the  physical 
chemists,  which  allow  water  to  pass  through  them  but  (as  commonly 
alleged)  no  dissolved  substances,  are  also  nothing  but  hydrated  colloid 
membranes.  None  of  them  are  really  impermeable  to  dissolved  sub- 
stances, but  they  allow  the  passage  of  such  only  very  slowly.  The 
oedematous  cell  dehydrated  from  within  may  therefore  swell  still 
more  if  water  is  given,  for  it  has  been  converted  into  a  series 
of  tiny  osmotic  systems,  in  other  words  droplets  of  concentrated 
salt  solution  in  semipermeable  bags  of  hydrated  colloid. 

These  remarks  must  not,  however,  be  misunderstood.  The 
normal  cell  is  no  such  system  and  the  play  of  osmotic  forces  within 
it  is  practically  zero. 

From  their  observations  on  oedema  the  clinicians  have  come 
to  the  false  conclusion  that  the  way  to  treat  it  is  to  withhold 
salt.  What  is  necessary  is  to  give  salt  but  to  withhold  water. 


§4 

We  may  now  return  to  the  general  question  of  the  possibilities 
for  the  development  of  osmotic  properties  by  any  cell  under 
physiological  or  pathological  circumstances. 

Obviously,  whenever  the  hydrated  protein  mass  moves  under 
the  influence  of  physiological  activity  or  in  consequence  of 
injury,  etc.,  in  the  direction  of  increased  hydration  and  increased 
solubility  in  water  it  moves  also,  in  the  direction  of  "  increased 
osmotic  pressure,"  increased  electrical  conductivity,  increased 
fluidity  and  decreased  viscosity;  while  changes  in  the  direction 
of  decreased  hydration  capacity  and  decreased  solubility  make 
for  an  opposite  set  of  changes.  It  is  well  to  bear  in  mind  the  simple 
nature  of  these  changes,  for  in  them  is  carried  the  "  explanation  " 
of  the  biological  terms  which  to-day  impede  progress  in  physiology 
or  pathology. 

1  See  page  113. 


248  SOAPS  AND  PROTEINS 

When  it  is  observed  that  the  colloid-chemical  interplay  between 
protein  colloids,  water  and  various  so-called  "  electrolytes  "  is 
governed  both  qualitatively  and  quantitatively  by  the  same  laws 
which  govern  various  physiological  functions  (like  water  absorp- 
tion, muscular  contraction,  nerve  conduction,  sense  of  taste, 
digestion,  enzymatic  reaction,  etc.)  it  follows  that  the  essence 
of  these  physiological  reactions  must  also  be  found  in  such  colloid- 
chemical  changes  in  the  protein  fraction  of  the  protoplasmic 
mass.  We  locate,  in  other  words,  the  portion  of  the  living  mass 
in  which  physiological  behavior  has  its  seat.  And  in  pathology, 
it  is  again  obvious  that  if  the  laws  governing  various  pathological 
changes  are  those  which  govern  the  colloid-chemical  behavior  of 
proteins  we  obtain  here,  too,  an  answer  to  the  nature  of  these 
changes  while  discovering,  at  the  same  time,  the  principles  which 
must  guide  us  in  their  treatment. 

Protoplasm  when  "  stimulated "  or  injured  manifests  sub- 
sequently a  "  current  of  action  "  or  "  reaction  to  injury."  Physio- 
logically we  know  that  the  irritated  or  injured  protoplasm  becomes 
more  acid,  that  its  electrical  potential  toward  an  uninjured  or  less 
injured  part  changes,  and  that  it  shows  an  increased  osmotic  pres- 
sure; pathologically  we  observe  the  injured  protoplasm  to  swell, 
to  undergo,  perhaps,  a  "  cloudy "  swelling  or  "  albuminous 
degeneration,"  which  when  sufficiently  severe  may  be  followed 
by  "  fatty  degeneration  "  and  death  of  the  involved  part  ("  necro- 
sis "). 

The  concepts  developed  in  the  preceding  pages  may  serve  to 
indicate  how  these  physiological,  anatomical  and  pathological 
entities  hang  together.  The  production  of  acid  in  a  part,  either 
through  activity  or  injury,  must,  of  necessity,  bring  with  it  an 
electrical  change,  succeeded  by  a  chemical  one  in  which  the  pro- 
teins of  the  involved  protoplasm  are  given  an  increased  hyd ra- 
tion capacity  and  so,  if  water  is  present,  are  made  to  swell.  Such 
swelling  will,  however,  be  manifested  only  by  proteins  of  the 
albumin  type.  The  globulins,  on  the  other  hand  (which  as 
sodium,  magnesium  or  calcium  globulinate  have  in  this  form  a 
higher  hydration  capacity),  will  be  robbed  of  their  bases,  and,  as 
the  less  hyd  ratable  "  free  "  "  globulinic  acid  "  tend  to  be  pre- 
cipitated. The  combination  yields  a  precipitated  material  within 
a  swollen  one,  in  other  words,  the  anatomical  picture  of  cloudy 
swelling.  But  the  swollen  proteins  are  also  more  soluble  in  water. 


SOAPS,  PROTEIN  DERIVATIVES  AND  TISSUES  249 

The  involved  protoplasm  will  therefore  not  only  tend  to  mix 
with  its  surrounding  medium,  but  (except  for  the  globulin  frac- 
tion) will  itself  be  moving  from  a  system  represented  by  a  solu- 
tion of  water  in  colloid  material  towards  a  system  represented 
by  a  true  solution  of  the  colloid  material  (the  protoplasm)  in  water. 
As  this  happens  there  will  be  observed  a  "  liquefaction  "  of  the 
protoplasm,  a  decrease  in  its  viscosity,  an  increased  diffusibility 
and  (if  such  diffusion  is  impeded  by  hydrated  colloid  walls)  mani- 
festations of  an  increased  osmotic  pressure. 

The  several  changes  described  make  for  a  steady  decrease  in 
the  amount  of  hydrophilic  colloid  present  in  the  unit  volume  of 
protoplasm  and  the  appearance  of  more  and  more  "  free  "  water. 
But  under  such  circumstance  any  fat  previously  held  apart  in 
finely  divided  form  within  the  protoplasm  begins  to  run  together 
into  larger  globules.  As  this  happens  we  get  the  anatomical  pic- 
ture of  "  fatty  degeneration." 

We  have  not  thus  far  considered  the  question  of  whether  a 
reversal  in  the  circumstances  producing  the  series  of  changes 
described  (with  their  accompanying  alterations  in  function)  allows 
these  changes  to  reverse  or  not.  If  reversion  is  possible  the  con- 
dition is  "  curable  ";  if  not,  the  involved  protoplasm  dies,  or,  to 
say  it  in  Greek,  it  suffers  necrosis. 

§5 

Considering  that  in  a  thousand  pages  of  pathology  the  sub- 
jects of  oedema,  cloudy  swelling  and  fatty  degeneration  scarcely 
take  up  a  dozen,  it  may  impress  the  reader  that  too  much  has  been 
made  of  them  in  the  pages  of  this  volume  and  preceding  ones.  If 
the  matter  needs  justification  then  it  is  written  in  the  fact  that  all 
disturbance  in  function  and  all  the  changes  of  disease  which  are 
reversible  and  therefore  curable  are  contained  within  the  confines 
of  these  lowly  concepts.  Cells  once  dead  may  be  replaced  by 
others,  but  the  physician  does  not  do  this.  If  he  has  a  problem 
it  is  that  of  how  to  maintain  the  physiological;  to  understand 
the  nature  of  the  pathological;  and  to  use,  not  with  hope  only, 
but  with  conscious  power  his  knowledge  of  these  things  in  order 
to  aid  nature  in  her  efforts  to  restore  an  injured  cell  to  the  normal. 

To  hasten  such  solution  our  efforts  have  not  brought  us  far. 
To  do  it  in  the  terms  of  morphology  is  to  end  in  pictures;  to  do 


250  SOAPS  AND  PROTEINS 

it  in  the  terms  of  pure  chemistry  is  to  end  in  formulae.  Perhaps 
to  do  it  in  the  terms  of  colloid-chemistry  as  attempted  in  the 
preceding  pages  is  also  inadequate,  but  if  it  is,  the  fault  is  resident 
in  the  misapplications  which  have  been  made,  not  in  the  inade- 
quacies of  colloid-chemistry  to  the  task. 


PART   FOUR 
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APPENDIX 


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256 


SOAPS  AND  PROTEINS 


II 

PHYSICO-CHEMICAL  CONSTANTS  OF  VARIOUS  ALCOHOLS  l 
1.  Monatomic  Alcohols  of  the  Formula  €^2,,+  iOH 


Alcohol. 

Formula 

Molecular 
weight. 

Specific 
gravity. 

Melting- 
point. 

Boiling- 
point. 

Methyl 

CHaOH 

32.03 

0.7913^ 

-   97.8° 

66.78° 

Ethyl 

CjHaOH 

46.05 

0.  785  HT*- 

-112.3° 

78.4° 

Propyl 

CiHrOH 

60.06 

0.80358^ 

97.4° 

Butyl 

C4H.OH 

74.08 

0.8138TS 

117.02° 

Amyl 

C5HuOH 

88.10 

0.816820 

137.8° 

Capryl 

Heptyl 

CrHuOH 

116.13 

0.83016 

-    36.5° 

175.8° 

Octyl 

CsHnOH 

130.15 

0.8375 

195.5° 

Nonyl 

Ci>H,9OH 

144.16 

0.8346^ 

-      5.0° 

215.0° 

Ethylene 

glycol 
Trimethylene 

glycol  * 


Glycerin 


CsH6(OH)2 


CsHs(OH)» 


2.  Diatomic  Alcohols 

62 . 05 
76.06 

3.  Triatomic  Alcohols 


-    17. 4< 


92.06 


120 
1 . 2604  ~-T 


17° 


4.  Other  Alcohols 


197.37° 
216.0° 


290.0° 


Allyl 

C»H6OH 

58.05 

0.8491^ 

-129° 

96.69° 

Benzyl  » 

CrHTOH 

108.06 

206  .  0° 

Cinnamyl 

C9H»OH 

134.08 

1.  0397^ 

33° 

257.5° 

1  Data  from  VAN  NOSTRAND'S  Chemical  Annual,  edited  by  JOHN  C.  OLSEN,  New  York 
(1913),  unless  otherwise  specified. 

*  V.  v.  RICHTER:    Organische  Chemie,  10fe  Aufl.,  1,  340  (1903). 

1  W.  H.  PERKIN  and  F.  STANLEY  KIPPING:  Organic  Chemistry,  451,  London  and  Edin- 
burgh (1911). 


BIBLIOGRAPHY 


The  following  is  a  list  of  publications  in  which  were  originally  expressed 
the  views  summed  up  in  running  form  in  the  foregoing  pages. 

1.  MARTIN  H.  FISCHER  and  MARIAN  0.  HOOKER:    On  the  Physical 

Chemistry  of  Emulsions  and  its  Bearing  upon  Physiological  and 
Pathological  Problems.     Science,  43,  468  (1916). 

2.  MARTIN  H.  FISCHER  and  MARIAN  0.  HOOKER:    Ueber  das  Entstehen 

und  Zergehen  von  Emulsionen.     Kolloid-Zeitschrift,  18,  129  (1916). 

3.  MARTIN  H.  FISCHER  and  MARIAN  0.  HOOKER:    Fats  and  Fatty 

Degeneration,  New  York  (1917). 

4.  MARTIN  H.  FISCHER  and  MARIAN  0.  HOOKER:    Ternary  Systems 

and  the  Behavior  of  Protoplasm.     Science,  48,  143  (1918). 

5.  MARTIN  H.  FISCHER:    Further  Studies  in  Colloid  Chemistry  and 

Soap.     Science,  49,  615  (1919). 

6.  MARTIN  H.  FISCHER  and  MARIAN  0.  HOOKER:    On  the  Hydration 

Capacity  of  Some  Pure  Soaps.     Chemical  Engineer,  27,  155  (1919). 

7.  MARTIN    H.    FISCHER:    Non-Aqueous    Lyophilic    Soap    Colloids. 

Chemical  Engineer,  27,  184  (1919). 

8.  MARTIN  H.  FISCHER  and  MARIAN  0.  HOOKER:    On  the  Colloid 

Chemistry  of  Potassium  Oleate  and  the  "  Salting-Out "  of  Soaps. 
Chemical  Engineer,  27,  223,  253  (1919). 

9.  MARTIN  H.  FISCHER:    On  the  Reaction  of  Soaps  to  Indicators. 

Chemical  Engineer,  27,  271  (1919). 

10.  MARTIN  H.  FISCHER:    Colloid  Chemistry  of  Soaps  and  Proteins. 

Proceedings  American  Society  of  Biological  Chemists,  5,  23  (1919). 

11.  MARTIN   H.    FISCHER   and   GEORGE   D.    MCLAUGHLIN:    A   Third 

Model  Illustrating  Some  Phases  of  Kidney  Secretion.    Journal 
of  laboratory  and  Clinical  Medicine,  5,  352  (1920). 


257 


AUTHOR  INDEX 


ARAKI,  T.,  242 


B 


BACHMANN,  W.,  6r  9 
BANCROFT,  WILDER  D.,  157 
BELL,  J.,  169 
BLYTH,  W.,  169 
BOSWORTH,  A.  W.,  228 
BOTAZZI,  F.,  6,  9,  110,  112 
BOWDEN,  R.  C.,  180 
BUGARSKY,  S.,  227 


CALVIN,  J.  W.,  218 
CHEVREUL,  3,  180 
CLOWES,  G.  H.  A.,  Ill,  112,  113, 
CORNISH,  C.  C.  V.,  180 

D 
DONNAN,  F.  G.,  157 

E 
ELSDON,  167,  168 


157 


FARNSTEINER,  165,  166 

FISCHER,  MARTIN  H.,  9,  30,  64 
75,  81,  82,  93,  110,  115,  138, 
155,  156,  218,  219,  230,  241, 
243,  257 

FODOR,  A.,  240 

FREUNDLICH,  H.,  65 

FRIEDLANDER,  J.,  66,  68,  69 


GOLDSCHMIDT,  F.,  6,  9,  111,  112, 

165,  181 

GRAHAM,  THOMAS,  76 
GRtissNER,  165,  166 


,  73, 
150, 
242, 


157, 


H 

HANDOVSKY,  H.,  218 
HARDY,  W.  B.,  66,  69,  218,  227 
HAZURA,  165,  166 
HEYERDAHL,  166 
HILLYER,  H.  W.,  157 

HOFMEISTER,    FRANZ,    6,    9,    110,    111, 

218,  245 
HOOKER,  MARIAN  O.,  9,  30,  64,  73, 

75,  93,  110,  115,  138,  150,  155,  156, 

230,  243,  257 
HOPPE-SEYLER,  F.,  242 
HOWELL,  W.  H.,  234 


IRASAWA,  T.,  242 


JUILLARD,  166 


K 


KEHOE,  ROBERT  A.,  237,  239,  240, 

241 

KIPPING,  F.  STANLEY,  256 
KRAFFT,  F.,  6,  9,  70,  110,  112,  166, 

180,  181,  206,  232 
KREBITZ,  P.,  191 
KRONACHER,  R.  J.,  117 


LACQUEUR,  E.,  228 
LEIMDORFER,  J.,  6,  9,  117,  174,  181 
LEWKOWITSCH,  J.,  7,  9,  165,  166,  167, 
168,  169,  206,  254 

LlEBERMANN,  L.,  227 

LINK,  168 

LLOYD,  JOHN  URI,  243,  244 

LONG,  C.  P.,  192 

M 

MACNlDER,  W.  DEB.,  242 

MATHEWS,  A.  P.,  69 


259 


260 


AUTHOR  INDEX 


McBAiN,  JAMES  W.,  Ill,  112 
MCLAUGHLIN,  GEORGE  D.,  257 
MEISSL,  169,  170 
MERKLEN,  F.,  165 
MUNSON,  165,  166 


X 


NOTES,  A.  A.,  65 


OLSEN,  JOHN  C.,  253,  256 
OSTWALD,  WALTHER,  157 
OSTWALD,  WOLFGANG,  64,  65,  66,  68, 
69,  209,  218,  226 


PAULI,  WOLFGANG,  218,  219,  227 
PAULMYER,  167 
PERKIN,  W.  H.,  256 
PERRIN,  J.,  65 
PICKERING,  S.  U.,  157 
PLATEAU,  S.,  157 


Q 


QUINCKE,  G.,  157 

R 

REICHERT,  169,  170 
RICHTER,  V.  VON,  253,  256 
RINGER,  236 

ROBERTSON,  T.  B.,  157,  228 
ROTHMUND,  V.,  66,  68,  69 


S 

SACKUR,  O.,  228 
SALMON,  C.  S.,  157 
SCHORR,  KARL,  218 
SCHROEDER,  P.  VON,  218 
SHORTER,  S.  A.,  157 
SMITS,  A.,  181 
SPALLANZANI,  169 
SPIRO,  K.,  218 

STIEPEL,  C.,  117,  182,  .188,  189 
STUBEL,  234 

T 

TAYLOR,  MILLICENT,  111,  112,  180 
TOLMAN,  165,  166 
TWITCHELL,  ERNST,  5,  6,  165,  168 

U 

UBBELOHDE,  157,  165 
UPSON,  F.  W.,  218 


VAN  SLYKE,  L.  L.,  228 
VICTOROW,  C.,  6,  9,  110,  112 

W 

WATT,  ALEXANDER,  174 
WEIMARN,  P.  P.  VON,  65,  69 
WEISS,  H.  B.,  242,  243 
WEISSMANN,  L.,  6,  9,  111,  112,  181 
WIGLOW,  H.,  6,  9,  110,  180,  181,  206 
WOOD,  T.  B.,  218 


ZILLESSEN,  HERMANN,  242 


SUBJECT   INDEX 


A 

ACETIC  ACID,  7,  253. 

ACETIC  SERIES,  fatty  acids  of,  7,  253;  soaps  of,  16. 

ACETIC  SERIES  SOAPS,  16,  salting-out  of,  117,  135;  gelation  of,  135;  and  foam- 
ing characteristics,  138,  141;  and  emulsifying  characteristics,  136,  150; 
and  washing  characteristics,  136,  157. 

ACID,  acetic,  7,  253;  butyric,  7,  253;  valeric,  7,  253;  caproic,  7,  253;  caprylic, 
7,  253;  capric,  7,  253;  lauric,  7,  253;  ficocerylic,  7;  myristic,  7,  253; 
isocetic,  7;  palmitic,  7,  253;  margaric,  7,  253;  stearic,  7,  253;  arachidic, 
7,  253;  behenic,  7,  253;  lignoceric,  7;  carnaubic,  7;  pisangcerylic,  7; 
cerotic,  7,  253;  montanic,  7;  melissic,  7;  psyllostearylic,  7;  tiglic,  7, 
254;  hypogaeic,  7,  254;  physetoleic,  7,  254;  palmitoleic,  7,  254;  lyco- 
podic,  7,  254;  oleic,  7,  254;  elaidic,  7,  254;  isooleic,  7,  254;  rapic,  7, 
254;  petroselinic,  7,  254;  cheiranthic,  7,  254;  liver  oleic,  7,  254;  doeglic, 
7,  254;  jecoleic,  7,  254;  gadoleic,  7,  254;  erucic,  7,  254;  brassidic,  7,  254; 
isoerucic,  7,  254;  linolic,  8,  255;  millet  oil,  8,  255;  telfairic,  8,  255; 
elaeomargaric,  8,  255;  elaeostearic,  8,  255;  tariric,  8;  hydnocarpic,  8; 
chaulmoogric,  8;  linolenic,  8;  isoUnolenic,  8;  jecoric,  8;  isanic,  8; 
therapic,  8;  clupanodonic,  8;  arachidonic,  8;  sabinic,  8;  juniperic,  8; 
lanopalmic,  8;  coceric,  8;  ricinoleic,  8;  isoricinoleic,  8;  ricinelaidic,  8; 
ricinic,  8;  quince  oil,  8;  dihydroxystearic,  8;  lanoceric,  8;  hepta- 
decamethylenedicarboxylic,  8;  octodecamethj'lenedicarboxylic,  8;  jap- 
anic,  8;  formic,  253;  propionic,  253;  heptylic,  253;  hyaenic,  253;  pel- 
largonic,  253. 

ACIDS,  fatty,  7,  8,  253;  of  the  series  CnH2n+iCOOH,  20;  amins  of  fatty,  206; 
solubility  of  fatty  in  and  for  water,  206;  and  union  with  proteins,  227. 

ACID  SOAP,  112. 

ACRYLIC  ACID  SERIES,  7,  254. 

ADDITIVE  SALT  EFFECTS,  102. 

ADSORPTION,  in  soap  systems,  185. 

ALBUMIN  CONTENT  OF  SECRETIONS,  246. 

ALBUMINOUS  DEGENERATION,  248. 

ALBUMINURIA,  246. 

ALCOHOLS,  ethyl,  30,  31,  34,  56,  57;  amyl,  34,  56,  57;  capryl,  34,  56,  57; 
heptyl,  34,  56,  57;  methyl,  34,  56,  57;  octyl,  34,  56,  57;  nonyl,  34,  56,  57; 
propyl,  34,  56,  57;  monatomic,  44,  56;  allyl,  49,  53;  benzyl,  49,  58; 
cinnamyl,  49;  diatomic,  50,  58;  triatomic,  52,  59;  and  sodium  oleate, 
46;  and  sodium  elaldate,  46;  and  sodium  erucate,  47;  and  sodium  linolate, 
48. 

ALCOHOL/ SOAP  SYSTEMS,  30. 

ALKALIES,  and  salting-out  effects  on  potassium  oleate,  120,  121;  and  union 
with  proteins,  227;  and  heavy  metal  poisoning,  241, 

261 


262  SUBJECT  INDEX 

ALKALOIDS,  and  protoplasm,  244. 

ALLYL  ALCOHOL,  49,  53,  256. 

AMINO-ACIDS,  205. 

AMINO-FATTY-ACIDS,  206. 

AMMONIUM  linolate,  24;  oleate,  25;  stearate,  26;  palmitate,  27;  laurate,  28. 

AMMONIUM  CHLORID,  and  salting-out  of  soaps,  121,  130. 

AMMONIUM  HYDROXID,  and  salting-out  of  soaps,  121. 

AMYL  ACETATE,  61. 

AMYL  ALCOHOL,  34,  56,  57,  256. 

ANALOGIES,  in  colloid-chemistry  of  protein  derivatives  and  tissues,  205. 

ANTIDOTES,  241. 

ARACHIDIC  ACID,  7,  253. 

ARACHIDONIC  ACID,  8. 

ASBESTOS,  193. 

B 

BARIUM  linolate,  24,  oleate,  25,  stearate,  26,  palmitate,  27,  laurate,  28. 
BARYTES,  193. 
BEESWAX,  169. 
BEHENIC  ACID,  7,  253. 
BENZALDEHYD,  61,  63. 
BENZENE,  61,  63. 
BENZYL  ALCOHOL,  49,  58,  256. 
BIBLIOGRAPHY,  257. 
BIOLOGICAL  COAGULATIONS,  233. 
BLOOD  COAGULATION,  233. 
BORAX,  as  soap  filler,  185. 
BRASSIDIC  ACID,  7,  254. 
BRINE,  and  salting-out  of  soaps,  182. 
BUTTER  FAT,  168. 
BUTYL  (Iso)  ALCOHOL,  56,  57,  256. 
BUTYRIC  ACID,  7,  253. 

C 

CACAO  BUTTER,  167. 

CALCIUM  CHLORID,  and  salting-out  of  soaps,  131. 
CALCIUM  HYDROXID,  in  soap  manufacture,  93. 

CALCIUM  linolate,  24;  oleate,  25;  stearate,  26;  hydroxid,  93;  chlorid,  131. 
CAPRIC  ACID,  7,  253. 
CAPROIC  ACID,  7,  253. 
CAPRYL  ALCOHOL,  34,  56,  57,  256. 
CAPRYLIC  ACID,  7,  253. 
CARBON  TETRACHLORID,  61,  63. 
CARNAUBIC  ACID,  7. 
CASEIN,  228,  233;  systems,  288. 
CASEINOGEN,  coagulation  of,  233. 
CASTOR  OIL,  166. 

CELLS,  osmotic  phenomena  in,  247. 
CEROTIC  ACID,  7,  253. 
CHALK,  193. 
CHAULMOOGRIC  ACID,  8. 
CHAULMOOGRIC  ACID  SERIES,  8. 
CHEIRANTHIC  ACID,  7,  254. 
CHLOROFORM,  61,  63. 


SUBJECT  INDEX  263 

CINNAMYL  ALCOHOL,  49,  256. 

CLAY,  193. 

CLOUDY  SWELLING,  248. 

CLUPANODONIC  ACID,  8. 

CLUPANODONIC  ACID  SERIES,  8. 

COAGULATION,  225;  definition  of,  226;  of  protein  systems,  230;  through 
heat,  230. 

COCOANUT  OIL,  167. 

COCCERIC  ACID,  8. 

COD  LIVER  OIL,  166. 

COLD  PROCESS  SOAP  MANUFACTURE,  170. 

COLD  WATER  SOAPS,  187. 

COLLOIDS,  definition  of  lyophilic,  64;  theory  of,  64;  classification  of,  64; 
lyophobic,  65;  difference  between  lyophilic  and  lyophobic,  65;  lyophilic 
and  lyophobic,  72;  hysteresis,  swelling,  liquefaction,  gelation  capacity, 
solvation  capacity,  syneresis  and  sols  of,  74;  swelling  of,  75;  sweating  of, 
76;  as  fillers  for  soaps,  193. 

COLLOID-CHEMICAL  CHANGES,  and  physiological  reactions,  248. 

COLLOID-CHEMISTRY,  of  soap-making,  6;  of  protein  derivatives,  208;  of  deriva- 
tives of  egg-globulin,  210. 

COLLOID  IONS,  112. 

COLLOID  SYSTEMS,  stabilization  of,  225;  reaction  of,  to  indicators,  229. 

COMPARISON,  of  soaps,  23;  of  soap  systems  with  gelatin  systems,  223;  of 
soap  systems  with  protein  systems,  223. 

CONSTANTS,  of  fats  and  oils,  169;  of  market  soaps,  186;  of  fatty  acids,  253; 
of  alcohols,  256. 

CONVERSION,  of  one  soap  into  another,  190;  of  heavy  metal  proteinates  to 
light  metal  proteinates,  237. 

COTTONSEED  OIL,  165;  saponification  of,  172. 

CRITICAL  MIXTURES,  66. 

CRITICAL  TEMPERATURE,  68. 

CUPRIC  CHLORID,  and  salting-out  of  soaps,  132. 

CUPRIC  SULPHATE,  238. 

CURABILITY,  249. 

CURD  SOAP,  181,  183. 

CURRENT  OF  ACTION,  in  protoplasm,  248. 

CYCLIC  ACIDS,  8. 

D 

DEATH,  248. 

DEHYDRATION,  by  sodium  chlorid,  246. 
DEPRIVATION  OF  SOLVENT,  245. 
DIA.TOMIC  ALCOHOLS,  50,  58,  256. 
DIBASIC  ACIDS,  8. 

DlHYDROXYLATED  AdDS,  8. 
DlHYDROXYSTEARIC  AdD,  8. 

DIPHASIC  SYSTEMS,  viscosity  of,  115. 
DOEGLIC  ACID,  7,  254. 
DRYING  OF  SOAPS,  189,  191 

E 

EGG-GLOBULIN,  and  hydroxids,  207;  and  water  systems,  209;  colloid-chem- 
istry of  derivatives  of,  210;  and  acids,  212;  and  salts,  217. 


264  SUBJECT  INDEX 

El^EOMARGARIC  ACID,  8,  255. 

EI^EOSTEARIC  ACID,  8,  255. 

ELAIDIC  ACID,  7,  254. 

EMULSIFICATION,  theory  of,  154;  in  soap  manufacture,  174. 

EMULSIFYING  PROPERTIES  OF  SOAPS,  136,  150. 

EMULSION,  73. 

ENZYMES,  and  heavy  metal  action,  239;  and  degree  of  dispersion,  240. 

ERUCIC  ACID,  7,  254. 

ETHERS,  61. 

ETHYL  ALCOHOL,  34,  56,  57,  256;  and  soap  systems,  30,  34. 

ETHYL  ALCOHOL/SODIUM  OLEATE  SYSTEMS,  31. 

ETHYL  (ENANTHATE,  61,  63. 

ETHYLENEGLYCOL,  50,  58,  59,  256. 

EUTECTIC  MIXTURES,  20. 

F 

FAT  CONSTANTS,  169. 

FATS,  3;  in  soap  making,  164. 

FATTY  DEGENERATION,  248. 

FERRIC  CHLORID,  and  salting-out  of  soaps,  133. 

FERRIC  SULPHATE,  238. 

FIBRINOGEN,  coagulation  of,  233. 

FICOCERYLIC  ACID,  7. 

FILLED.  SOAPS,  185. 

FILLER  FOR  SOAPS,  borax  as,  185;    sugar  solution  as,  192;    colloids  as,  193; 

nature  of  action  of,  194;  use  of,  in  excess,  195. 
FINISHING  OF  SOAPS,  183. 
FLOUR,  193. 
FOAMING,  of  soaps,  136;  soaps  effective  for,  138;  effect  of  temperature  upon, 

138;  theory  of,  154. 

FOAMS,  solid,  136;  liquid,  136,  production  of,  137;  maintenance  of,  137. 
FORMIC  ACID,  253. 

G 

GADOLEIC  ACID,  7,  254. 

GAS  IN  GAS,  64. 

GAS  IN  LIQUID,  64. 

GAS  IN  SOLID,  64. 

GASOLINE,  61,  63. 

GEL,  21 ;  theory  of  soap,  69. 

GELATIN,  209,  218;  swelling  of,  75,  218;  and  water  systems,  218;  solution  of, 
218;  independence  of  swelling  and  solution  in,  219;  hydration  and  solu- 
tion of,  219;  liquefaction  of,  220;  and  alkali,  220;  and  acid,  220,  and 
salt,  221. 

GELATIN  CHLORID,  221. 

GELATIN/WATER  SYSTEMS,  218. 

GELATION  CAPACITIES,  74,  76;  of  sodium  soaps,  21. 

GLOBULINS,  and  heat  coagulation,  233. 

GLYCERIN,  59,  256. 

GOOSE  FAT,  168. 

GRAINED  SOAPS,  183. 

GRAINING  OP  SOAPS,  5. 

GUMMING  OP  SOAPS,  182. 


SUBJECT  INDEX  265 

H 

HALF-SETTLED  SOAPS,  183. 

HEAT  COAGULATION,  230;    of  protein  and  soap  systems,  231;    of  biological 

fluids,  233. 

HEAVY  METALS,  nature  of  poisoning  by,  241 . 
HEAVY  METAL  POISONING,  nature  and  relief  of,  241. 
HEAVY  METAL  PROTEIN ATES,  192,  237. 
HEPTADECAMETHYLENEDICARBOXYLIC  ACID,  8. 
HEPTANE,  61,  63. 
HEPTYL  ALCOHOL,  34,  56,  57,  256. 
HEPTYLIC  ACID,  253. 
HOG  FAT,  168. 

HOT  PROCESS  SOAP  MANUFACTURE,  170. 
HOT  WATER  SOAPS,  187. 
HYAENIC  ACID,  253. 
HYDNOCARPIC  ACID,  8. 
HYDRATES,  114,  115. 

HYDRATION,  of  gelatin,  219;  and  solution  of  proteins,  219. 
HYDROGEN  IONS,  of  protein/water  systems,  214. 
HYDROGENATED  COTTONSEED  OIL,  saponification  of,  173. 
HYDROGEN  ATION,  13. 
HYDROLYSIS,  of  soaps,  79. 
HYDROXIDS,  and  egg-globulin,  207. 
HYDROXYL  IONS,  of  protein/water  systems,  214. 
HYDROXYLATED  ACIDS,  8. 
HYGROSCOPIC  PROPERTIES,  of  soaps,  189. 
HYPOG^IC  ACID,  7,  254. 
HYSTERESIS,  74. 


INDICATORS,  77;  and  protein  systems,  229. 

INJURY,  to  protoplasm,  82. 

IODIN  VALUE,  170. 

IONIZ ATION,  in  protoplasm,  82,  243. 

IONS,  colloid,  112. 

ISANIC  ACID,  8. 

ISOBUTYL  ALCOHOL,  56,  57. 

ISOCETIC  ACID,  7. 

ISOERUCIC  ACID,  7,  254. 

ISOLINOLENIC  ACID,  8. 

ISOOLEIC  ACID,  8,  254 

ISORICINOLEIC  ACID,  8. 

ISOSMOTIC  SOLUTIONS,  236. 

ISOTONIC  SOLUTIONS,  236. 

J 

JAPAN  WAX,  168. 
JAPANIC  ACID,  8. 
JECOLEIC  ACID,  7,  254. 
JECORIC  ACID,  8. 
JELLYING,  of  soaps,  111. 
JUNIPERIC  ACID,  8. 

K 
KERNSEIFE,  183. 


266  SUBJECT  INDEX 

L 

LANOCERIC  Aero,  8. 
LANOPALMIC  ACID,  8. 
LARD,  168. 
LAURATES,  14,  28. 
LAURIC  ACID,  7,  253. 

LEAD  linolate,  24;  oleate,  25;  stearate,  26;  palmitate,  27;  laurate,  28. 
LEAD  CHLORID,  238. 
LEIMNIEDERSCHLAG,  183. 
LIGHT  METAL  PROTEINATES,  237. 
LIGNOCERIC  ACID,  7. 
LIMONENE,  61,  63. 

LlNOLATES,   10,  24. 

LINOLENIC  ACID,  8. 

LINOLENIC  ACID  SERIES,  8. 

LINO LIC  ACID,  8,  255. 

LINOLIC  ACID  SERIES,  8. 

LINSEED  OIL,  165. 

LIQUEFACTION,  74. 

LIQUID  FOAMS,  136. 

LIQUID  IN  GAS,  64. 

LIQUID  IN  LIQUID,  64. 

LIQUID  IN  SOLID,  64. 

LITHIUM  OLEATE,  25. 

LIVER  OLEIC  ACID,  7,  253. 

LYCOPODIC  ACID,  7,  254. 

LYE,  5,  181. 

LYOPHILIC  COLLOIDS,  71;  general  theory  of,  64;  definition  of,  64. 

LYOPHOBIC  COLLOIDS,  65,  72. 

M 

MAGNESIUM  linolate,  24;  oleate,  25;  stearate,  26;  palmitate,  27;  laurate,  28. 

MAGNESIUM  CHLORID,  and  salting-out  of  soaps,  131. 

MAGNESIUM  SULPHATE,  and  sodium  oleate,  200. 

MANUFACTURE,  of  soap,  163. 

MARGARIC  ACID,  7,  253;  as  eutectic  mixture,  20. 

MARINE  SOAPS,  187. 

MAYONNAISE,  115. 

MELISSIC  ACID,  7,  253. 

MERCURIC  CHLORID,  239. 

MERCURY  oleate,  25;  stearate,  26. 

METHYL  ALCOHOL,  34,  56,  57,  256. 

MILK  COAGULATION,  233. 

MILLET  OIL  ACID,  8,  255. 

MIXED  SYSTEMS,  73,  83,  84,  85,  86,  87,  88,  89. 

MON ATOMIC  ALCOHOLS,  44,  56,  256;  and  sodium  oleate,  46;  and  sodium 
elaidate,  46;  and  sodium  erucate,  47;  of  the  series  CnHnOH,  49;  con- 
stants of,  256. 

MONATOMIC  ALCOHOL/SOAP  SERIES,  30. 

MONTANIC  ACID,  7. 

MUTUAL  SOLUBILITY,  66. 

MYOBINOGEN,  coagulation  of,  233. 

MYRISTIC  ACID,  7,  253. 


SUBJECT  INDEX  267 

N 

NECROSIS,  248. 
NEUTRAL  SOAPS,  78. 

NON-AQUEOUS  SOLVENTS,  and  soap,  60,  63. 
NONYL  ALCOHOL,  34,  56,  57,  256. 
NUTMEG  BUTTER,  167. 

O 

OCTODECAMETHYLENEDICARBOXYLIC  AdD,  8. 
OCTYL  ALCOHOL,  34,  56,  57,  256. 
(EDEMA,  244;  action  of  sodium  chlorid  in,  246. 
OIL  CONSTANTS,  169. 
OILS,  3;  used  in  soap  making,  164. 
OLEATES,  10,  24. 
OLEIC  ACID,  7,  254. 
OLEIC  ACID  SERIES,  7,  254. 
OLIVE  OIL,  166. 
OPEN  CHAIN  ACIDS,  8,  255. 
OSMOTIC  SYSTEMS,  247;  nature  of,  247. 

P 

PALM  KERNEL  OIL,  167. 

PALM  OIL,  166. 

PALMITATES,  14,  27. 

PALMITIC  ACID,  7,  253. 

PALMITOLEIC  ACID,  7,  254. 

PARALDEHYD,  61,  63. 

PELARGONIC  ACID,  253. 

PEPTIZATION,  225;  definition  of,  226;  of  fatty  acids  and  proteins,  227. 

PETROSELINIC  ACID,  7,  254. 

PHENOL/ WATER  SYSTEMS,  66;  salting-out  of,  68. 

PHENOLPHTHALEIN,  78,  113. 

PHYSETOLEIC  ACID,  7,  254. 

PHYSICAL  STATE,  of  soap  mixtures,  83. 

PHYSICO-CHEMICAL  CONSTANTS,  of  fatty  acids,  253;  of  alcohols,  256. 

PHYSIOLOGICAL  REACTIONS,  and  colloid-chemical  changes,  248. 

PHYSIOLOGICAL  SALT  SOLUTION,  236. 

PINENE,  61,  63. 

PlSANGCERYLIC  ACID,  7. 

PLASMOLYSIS,  245. 

PLASMOPTYSIS,  245. 

PLUMBIC  CHLORID,  238. 

POISONING,  by  ammonium  compounds  and  heavy  metals,  235. 

POPPY  SEED  OIL,  165. 

POTASSIUM,  linolate,  24;  oleate,  25;  stearate,  26;  palmitate,  27,  laurate,  28; 

oleate,  93,  94,  95,  102,  108,  110,  120,  121,  127,  128,  129,  134,  135,  200,  201. 

hydroxid,  120,  127;    fluorid,  121;    chlorid,  122,  127,  128,  129;   bromid, 

122;   iodid,  122;   nitrate,  123;    sulphocyanid,  123;    sulphocyanate,  124; 

acetate,  125;  sulphate,  125;  tartrate,  126;  phosphate,  126,  citrate,  126; 

poisonous  action  of,  245. 
POTASSIUM  ACETATE,  125. 
POTASSIUM  BROMID,  122. 
POTASSIUM  CHLORID,  122,  127,  128,  129. 
POTASSIUM  CITRATE,  126. 


268  SUBJECT  INDEX 

POTASSIUM  FLUORID,  and  salting-out  of  soaps,  121. 

POTASSIUM  HYDROXID,  and  salting-out  of  soaps,  120,  127. 

POTASSIUM  IODID,  122. 

POTASSIUM  NITRATE,  123. 

POTASSIUM  OLEATE,  salting-out  of,  93;  effects  of  water  upon,  94;  effects  of 
alkalies  upon,  94;  effects  of  salts  upon,  95;  effects  of  alkali  and  salt 
together  upon,  108;  historical  remarks  on  the  salting-out  of,  110;  salting- 
out  effects  of  alkalies  upon,  120,  121,  127,  128,  129,  134,  135;  salting-out 
effects  of  neutral  salts  upon,  121,  122,  123,  124,  125,  126,  127,  128,  129, 
130,  131,  132;  and  sodium  carbonate,  200;  and  sodium  silicate,  201; 
and  sodium  borate,  201 ;  and  magnesium  sulphate,  201 . 

POTASSIUM  PHOSPHATE,  126. 

POTASSIUM  SOAPS,  16,  23;  foaming  properties  of,  143;  foaming  properties  of, 
of  the  acetic  series,  148. 

POTASSIUM  SULPHATE,  125. 

POTASSIUM  SULPHOCYANATE,  123,  124. 

POTASSIUM  TARTRATE,  126. 

POTATO  FLOUR,  193. 

PROPANDIOL  (1,  3),  50. 

PROPIONIC  ACID,  253. 

PROPYL  ALCOHOL,  34,  56,  57,  256. 

PROTEIN,  swelling  of,  75,  219;  acid  and  basic  derivatives  of,  206;  colloid- 
chemistry  of  derivatives  of,  208;  solution  of,  218;  action  of  acids  and 
alkalies  upon,  218;  salting-out  of,  226;  coagulation  of,  by  different 
bases,  230;  coagulation  of,  by  heat,  233;  and  heavy  and  light  metals,  237. 

PROTEIN  DERIVATIVES,  205;  solution  of,  205;  hydration  of,  205;  solubility 
of,  in  and  for  water,  206. 

PROTEIN  SYSTEMS,  compared  with  soap  systems,  223. 

PROTEIN/ WATER  SYSTEMS,  stability  of,  214;  independence  of  swelling  and 
solution  in,  219. 

PROTOPLASM,  solution  of  water  in,  78;  ionization  in,  82,  243;  injury  to,  82, 
247;  fundamental  chemical  constitution  of,  235;  as  solution  of  water  in, 
235;  effects  of  introducing  different  bases  into,  236,  237;  fundamental 
composition  of,  243;  salts  in,  243;  and  alkaloids,  244;  solubility  of,  for 
water,  244;  solubility  of,  in  water,  245;  reaction  of,  when  injured,  247; 
electrical  conductivity  of,  247;  cloudy  swelling  in,  248. 

PSYLLOSTEARYLIC  ACID,  7. 


QUINCE  OIL  ACID,  8. 


R 


REACTION  TO  INJURY,  in  protoi>lasm,  82,  248. 
RAPIC  ACID,  7,  254. 
REICHERT-MEISSL  VALUK,  170. 
REVERSIBILITY,  in  soaps,  89. 

RlCINELAlDIO  ACID,  8. 

RICINIC  ACID,  8. 
RICINOLEIC  ACID,  8. 
RICINOLEIC  ACID  SERIES,  8. 
RINOER  SOLUTION,  230. 


SUBJECT  INDEX  269 


SABINIC  ACID,  8. 

SALIVA,  and  heavy  metals,  240. 

SALTING-OUT,  of  soaps,  5,  68,  80,  93,  182;  of  phenol/water  system,  68;  of 
potassium  oleate,  93;  historical  remarks  on,  of  soaps,  107,  110;  theory 
of,  of  soaps,  113;  of  different  soaps,  116;  of  acetic  series  soaps,  117; 
effects  of  concentrations  of  sodium  chlorid  upon,  of  soaps,  117,  128,  129, 
130;  of  mixed  soaps,  181,  of  proteins,  226. 

SALTS,  effects  of,  on  potassium  oleate,  95;  water  attracting  power  of,  110,  111; 
and  gelatin,  222;  relation  of,  to  protoplasm,  243. 

SAPONIFICATION,  effect  of  concentration  of  alkali  upon,  179. 

SAPONIFICATION  VALUE,  170. 

SECRETIONS,  as  solutions  of  protoplasm  in  water,  235;  albumin  content  of,  246. 

SEED  HUSKS,  193. 

SESAME  OIL,  166. 

SETTLED  SOAP,  181,  183. 

SHAVING  SOAPS,  191. 

SILVER  NITRATE,  238. 

SOAP,  definition  of,  3;  graining  of,  5;  by  Twitchell  process,  5;  preparation 
of,  10. 

SOAPS,  gelation  capacities  of,  10;  with  different  basic  radicals,  10;  with  differ- 
ent acid  radicals,  15;  of  acetic  acid  series,  16;  and  water  concentration, 
22;  and  non-aqueous  solvents,  60,  63;  salting-out  of,  68;  as  normal 
electrolytes,  70,  180;  as  coUoids,  70,  112,  181;  neutral,  78,  113;  hydroly- 
sis of,  79;  reversibility  in,  89;  salting-out  of,  93,  182;  historical  remarks 
on  salting-out  of,  107,  110;  jellying  of,  111;  acid,  112,  113;  as  true 
solutions,  112;  alkaline  to  phenolphthalein,  113;  theory  of  salting-out 
of,  113;  salting-out  of  different,  116;  gelation  and  salting-out  of  various, 
of  tke  acetic  series,  135;  foaming  properties  of,  136;  emulsifying  proper- 
ties of,  136,  150;  washing  properties  of,  136,  157;  changes  in,  on  cooling, 
180;  salting-out  of  mixed,  181;  curd,  181,  183;  settled,  181,  183;  gram- 
ing  of ,  182,  183;  "going  stringy"  of,  182;  finishing  of ,  183;  half-settled, 
183;  filled,  185;  transparent,  186;  physical  constants  of  market,  186; 
cold  water,  187;  hot  water,  187,  marine,  187;  hygroscopic  properties  of, 
189;  water  loss  by,  189;  conversion  of  one  into  another,  190;  shaving, 
191;  fillers  for,  192;  hydrolysis  in,  231;  heat  coagulation  of,  231,  232. 

SOAP/ ALCOHOL  SYSTEMS,  30;  with  different  soaps,  31;  with  different  alco- 
hols, 31. 

SOAP  GELS,  as  mutually  soluble  systems,  66,  69;  theory  of,  69. 

SOAP  IN  WATER,  69. 

SOAP  KETTLE,  164. 

SOAP  MAKING,  6. 

SOAP  MANUFACTURE,  163;  by  cold  process,  170;  by  hot  process,  170;  mixing 
of  fat  with  alkali  in,  174;  emulsification  in,  174;  microscopic  changes 
observed  during,  176;  addition  of  alkali  in,  178. 

SOAP  MIXTURES,  83. 

SOAP  SYSTEMS,  effects  of  temperature  on,  71;  compared  with  gelatin  systems, 
223. 

SOAP/WATEK  SYSTEMS,  9. 

SODIUM  caproate,  17,  19,  38,  54,  56,  58;  caprate,  19,  39,  54,  56,  58;  laurate,  19, 
28,  39,  54,  56,  58,  59;  myristate,  19,  40,  54,  56,  58,  59;  palmitate,  19,  27, 
41,  54,  56,  58,  59;  arachidate,  20,  54;  margarate,  20,  42,  54,  56;  stearate, 
20,  26,  43,  54,  56,  58,  59:  elaidate,  21,  55,  57,  58,  59;  erucate,  21,  58,  59; 


270  SUBJECT  INDEX 

linolate,  21,  24,  57;  oleate,  21,  25,  55,  57,  58,  59;  acetate-alcohol  systems, 
31;  butyrate-alcohol  systems,  31 ;  caproate-alcohol  systems,  31;  caprate- 
alcohol  systems,  31;  capry late-alcohol  systems,  31;  erucate-alcohol  sys- 
tems, 35;  elaidate-alcohol  systems,  35;  caprylate,  38,  54,  56,  58;  elaidate 
and  different  alcohols,  46;  oleate  and  different  alcohols,  46;  erucate  and 
different  alcohols,  47;  linolate  and  different  alcohols,  48;  butyrate,  54, 
56;  valerate,  54;  acetate,  55;  formate,  55;  propionate,  55;  oleate  and 
indicators,  78;  stearate  and  indicators,  79;  oleate-sodium  stearate  mix- 
tures, 83,  84,  88;  oleate-sodium  palmitate  mixtures,  83,  85,  88;  linolate- 
sodium  stearate  mixtures,  86,  88;  caprylate-sodium  stearate  mixtures, 
87,  89;  chlorid,  117,  128,  129,  130,  185,  246;  hydroxid,  120;  carbonate 
as  soap  filler,  185;  borate  as  soap  filler,  185;  silicate  as  soap  filler,  185; 
gelatinate,  221;  caseinate,  229. 

SODIUM  ACETATE,  55;  -alcohol  systems,  31. 

SODIUM  ARACHIDATE,  20,  54. 

SODIUM  BORATE,  as  soap  filler,  185;  and  sodium  oleate,  199. 

SODIUM  BUTYRATE,  54,  56;  -alcohol  systems,  31. 

SODIUM  CAPRATE,  19,  39,  54,  56,  58;  -alcohol  systems,  31. 

SODIUM  CAPROATE,  17,  19,  38,  54,  58;  -alcohol  systems,  31. 

SODIUM  CAPRYLATE,  38,  54,  56,  58;  -alcohol  systems,  31;  -sodium  stearate 
mixtures,  87,  89. 

SODIUM  CARBONATE,  as  soap  filler,  185;  and  sodium  oleate,  198. 

SODIUM  CASEINATE,  229. 

SODIUM  CHLORID,  and  sodium  soaps,  80;  effects  of  concentrations  of,  for 
salting-out  of  soaps,  117,  128,  129,  130;  as  soap  filler,  185;  and  dehy- 
dration of  protoplasm,  246. 

SODIUM  ELAIDATE,  21,  55,  57,  58,  59;  -alcohol  systems,  35;  and  different 
alcohols,  46. 

SODIUM  ERUCATE,  21,  58,  59;  -alcohol  systems,  35;  and  different  alcohols, 
47. 

SODIUM  FORMATE,  55. 

SODIUM  GELATINATE,  221. 

SODIUM  HYDROXID,  and  salting-out  of  soaps,  120. 

SODIUM  LAURATE,  19,  28,  39,  54,  56,  58,  59. 

SODIUM  LINOLATE,  21,  24,  57;  and  different  alcohols,  48;  -sodium  stearate 
mixtures,  86,  88. 

SODIUM  MARGARATE,  20,  42,  54,  56. 

SODIUM  MYRISTATE,  19,  40,  54,  56,  58,  59. 

SODIUM  OLEATE,  21,  25,  55,  57,  58,  59;  and  ethyl  alcohol,  31;  and  different 
alcohols,  46;  and  indicators,  78;  -sodium  stearate  mixtures,  83,  84,  88; 
-sodium  palmitate  mixtures,  83,  85,  88;  and  sodium  carbonate,  198; 
and  sodium  silicate,  199,  201;  and  sodium  borate,  199;  and  magnesium 
sulphate,  200. 

SODIUM  PALMITATE,  19,  27,  41,  54,  56,  58,  59;  -sodium  oleate  mixtures,  83, 
85,88. 

SODIUM  PROPIONATE,  55. 

SODIUM  SILICATE,  as  soap  filler,  185;  and  sodium  oleate,  199,  201. 

SODIUM  SOAPS,  16,  23;  of  the  acetic  acid  series,  29,  44;  of  the  oleic  acid 
series,  29;  of  the  linolic  acid  series,  29;  and  diatomic  alcohols,  50;  and 
triatomic  alcohols,  52;  and  glycerin,  52;  and  ethyl  alcohol,  54;  and 
alkali,  80;  and  sodium  chlorid,  80;  foaming  properties  of,  139;  produc- 
tion from  potassium  soaps,  190;  production  from  calcium  soaps,  191; 
production  from  ammonium  soaps,  191. 


SUBJECT  INDEX  271 

SODIUM  STEARATE,  20,  26,  43,  54,  56,  58,  59;  and  indicators,  79;  -sodium 
oleate  mixtures,  83,  84,  88;  -sodium  linolate  mixtures,  86,  88;  -sodium 
caprylate  mixtures,  87,  88. 

SODIUM  VALERATE,  54. 

SOFT  SOAP,  83. 

SOL,  74,  76. 

SOLID  FOAMS,  136. 

SOLID  IN  GAS,  64. 

SOLID  IN  LIQUID,  64. 

SOLID  IN  SOLID,  64. 

SOLID  TISSUES,  81. 

SOLUBILITY,  mutual,  66. 

SOLUTION,  17;  definition  of,  69,  221;  of  proteins,  218. 

SOLVATES,  114,  115. 

SOLVATION  CAPACITY,  74,  76. 

SOLVENT,  deprivation  of,  245. 

SOLVENTS,  30. 

STARCH,  193. 

STEARATES,  10,  26;  reversion  of,  from  heavy  to  light  metal  soaps,  92. 

STEARIC  ACID,  7,  253. 

STIMULATION,  of  protoplasm,  248. 

SUGAR  SOLUTIONS,  as  fillers  for  soaps,  191. 

SUSPENSION,  73. 

SWEATING,  of  colloids,  76. 

SWELLING,  74,  75;  of  protein,  218. 

SYNERESIS,  17,  30,  74,  76. 

SYSTEM,  soap/water,  9;  soap/alcohol,  30;  soap/x,  60;  phenol/water,  66; 
gelatin/water,  218;  casein/water,  228. 

SYSTEMS,  viscosity  of  diphasic,  115;  stabilization  of,  225;  osmotic,  247. 

T 

TALLOW,  168. 

TAPIOCA,  193. 

TARIRIC  ACID,  8. 

TARIRIC  ACID  SERIES,  8. 

TELFAIRIC  ACID,  8,  255. 

THEORY,  of  salting-out  of  soaps,  113;  of  washing,  157;  of  emulsification,  157. 

THERAPIC  ACID,  8. 

TIGLIC  ACID,  7,  254. 

TIME,  as  factor  in  production  of  colloid  systems,  198. 

TISSUES,  205. 

TOLUENE,  61,  63. 

TRANSPARENT  SOAPS,  186. 

TRIACETIN,  61,  63. 

TRI ATOMIC  ALCOHOLS,  52,  59,  256. 

TRIMETHYLENEGLYCOL,  50,  58,  59,  256. 

TURGOR,  244. 

TURPENTINE,  61,  63. 

TWITCHELL  PROCESS,  5. 

V 

VALERIC  ACID,  7,  253. 
VARIABLES  in  soap  vat,  4. 
VISCOSITY,  of  mixed  systems,  115. 


272  SUBJECT  INDEX 

W 

WASHING  PROPERTIES,  of  soaps,  136,  157. 
WATER-ATTRACTING  POWER,  of  salts,  110,  111. 
WATER  DISSOLVED  IN  X,  81. 
WATER/EGG-GLOBULIN  SYSTEMS,  209. 
WATER/GELATIN  SYSTEMS,  218. 
WATER-GLASS,  185,  as  soap  filler,  185. 
WATER  IN  SOAP.  69. 
WATER  Loss,  by  soaps,  189. 
WAXES,  used  in  soap  making,  164. 
WHEAT  GLUTEN,  218. 


X  DISSOLVED  IN  WATER,  81. 
XYLENE,  61,  63. 


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